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UBRARY'OF CONGRESS. 



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UNITED STATES OF AMERICA. 



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LABORATORY COURSE 



IN 



INVERTEBRATE ZOOLOGY 



BY^ 



HERMON C. BUMPUS, Ph.D. 

Professor of Comparative Anatomy in Brown University, Providence, R.I., 
Instructor at the Marine Biological Laboratory, Woods Holl, Mass. 



SECOND EDITION, REVISED 




NEW YORK 

HENRY HOLT AND COMPANY 

1893 



.rc/iyj 



QLS-3 



Copyright, iSge, 
By HERMON C. BUMPUS. 



Copyright, 1893, 
By henry holt & CO. 




Typography by J. S. Gushing & Co., Boston. 



PREFACE. 



In the preparation of this book the author has had in 
mind the requirements of a class of students who are 
pursuing a course of laboratory work in Invertebrate 
Zoology. An effort has been made to direct the work, 
without, at the same time, actually telling the student all 
that there is to be learned from the specimen. It is 
taken for granted that an instructor is present to assist 
when there is trouble, and to demonstrate many things 
that written descriptions might only render more con- 
fusing. 

The animals that have been selected are not always 
the most typical, but they are generally forms that can 
easily be secured and preserved. 

In the Appendix a few words have been given regard- 
ing laboratory methods, etc. It has not been thought 
advisable to introduce any considerable treatment of the 
microscope as an optical instrument, nor have the modern 



iv Preface, 

and valuable methods of microscopical research been more 
than outlined. The former will be found in numerous 
text-books ; for the latter, it is expected that the stu- 
dent will consult Whitman's *^ Methods of Microscopical 
Anatomy and Embryology " and Lee's " Microtomists' 
Vade-Mecum." 

Providence, R.I., 
March, 1892. 



CONTENTS. 



PAGE 

Preface iii 

Protozoa — 

Amoeba I 

Paramoecium 3 

CCELENTERATA — 

Leucosolenia 5 

Grantia 9 

Campanularia 12 

Pennaria o 17 

Metridiu77i » 19 

Cyanea 23 

Mnemiopsis 26 

ECHINODERMATA — 

Asterias 29 

Arbacia 2>Z 

Thy one 36 

Vermes — 

Bdelloura 39 

Nereis 42 

Bugula 47 

Phascolosoma 51 

V 



VI Contents, 

MOLLUSCA — 

PAGE 

Venus 

53 

Sycotypus, ^^ 

Loligo ^Q 

Crustacea — 

Homarus ^o 

1^ 

Branchipus 

Cyclops ^^ 

Pandarus o 

9^ 

^'P""' » lOI 

Cancer 

Talorchestia 

LiMULUS AND ArACHNOIDEA — 

Limulus 

^P^ira J jg 

Antennata — 

Sphinx ^ 

Acridium ^ ^^ 

129 

Molgula , 

ApPExNDIX 

A. Use of Laboratory and Laboratory Apparatus 143 

B. List of Instruments and Reagents 14c 

C. Microscopes j^ 

D. Directions for Dissection j .g 

E. Methods of Killing, Fixing, and Hardening i^o 

F. Methods of Preservation I c j 

G. Methods of Staining jcj 

H. Methods of Mounting ^^^ 

I. Methods of Imbedding and Section Cutting 153 



INVERTEBRATE ZOOLOGY. 



o>«<o 



A RHIZOPOD PROTOZOAN 

{Amoeba sp?). 

Place a drop of water that is known to contain AmcebcB 
upon a slide and cover with a thin cover-glass. Having 
found an Ainoeba^ note the following points : 

The outline is irregular, and, if the animal is active, con- 
stantly changing. The ray-like prolongations of the body 
are called pseudopodia. Are the pseudopodia simple, or are 
they branched? How many are there ? 

The body of the animal is apparently made up of two 
portions, — an inner granular portion, the eiidosarc, and an 
outer clear layer, the ectosarc. Is there endosarc in the 
pseudopodia? Careful observation will reveal the presence 
of a circulation of the granules of the endosarc. 

Examining the endosarc with more care, it will be found 
to Q,ow\2\x\ food vacuoles^ a vesicle^ and a nicclcus, 

"W^t food vacuoles are small, generally spherical bodies, in 
color depending on the food that has been ingested. Around 
certain vacuoles a clear enveloping space may be noted. 

The 7iuc/eus, not often clearly seen in the living animal, 
may be definitely demonstrated by adding a drop of one per 



2 Invertebrate Zoology. 

cent acetic acid to the water holding the Amxba, The acid 
kills the animal and colors the nucleus light brown. 

Make drawings illustrating the points above considered. 

Observe a living specimen as it crawls about, and see if it 
advances one portion of its body in preference to another. 
Jar the slide. Is the animal sensitive ? If possible, observe 
the animal feed. It may be fed with powdered carmine, 
indigo, or Bismarck brown. 

At times, by a process of fission, or self- division, the 
Amoeba divides into two smaller Amoebce, which may in turn 
again divide. This method of multiplication is asexual. 



A Ciliate Protozoan, 



A CILIATE PROTOZOAN 

(Paramcedum caudatum). 

Prepare slides in the same way as was directed for 
A?7iceba, If the animals have been fed for some hours with 
carmine or Bismarck brown, the internal structure will often 
be more clearly shown. 

Under the compound microscope the Paramoecia are seen 
to gUde rapidly about, lashing their way through the water 
by means of innumerable cilia. Have they an ariteiHor and 
a posterior end ? Find an animal that is quiet, and see if 
you can distinguish between an external me7nbrane and the 
enclosed granular cytoplasm. 

Are all the ciha of about the same length ? Note their 
arrangement along the edges of the opening that leads into 
the animal from the side. This opening leads into the 
vestibuk. 

The vestibule is the ciliated passage down which food is 
forced on its way to the cytoplasm. Is there a definite flow- 
ing of the cytoplasm ? Are the contained food vacuoles dif- 
ferent from those of the Amxba ? The food-balls, after 
losing their nutritious portions, are ejected from the body at 
a point, the anus^ situated a little way posterior to the vesti- 
bule. 

Do you find pulsating vacuoles ? How many ? What is 
the outline in diastole ? In systole ? 



4 Invertebrate Zoology, 

Use dilute acetic acid, and note the form and arrangement 
of the trichocysts, defensive bodies comparable to the nema- 
tocysts of Coelenterates. 

A ciliate infusorian contains a macronucleus and one or 
more micronuclei. The former is a comparatively large 
body and can readily be observed by the use of dilute acetic 
acid. The micronuclei are smaller and, in some cases, diffi- 
cult to find. 

Paramcecia are often to be observed attached in pairs by 
their vestibular surfaces, in process of conjugation. After 
remaining attached for some little time, the two become 
free and undergo division hy fission} 

Make a drawing of Fara^noecitim, naming the parts. 

1 Conjugation is completed by disappearance of the macronuclei, which 
are supposed to be nutritive bodies for use during this period of inac- 
tivity. The micronuclei, during conjugation, are actively dividing, and 
previous to separation one of these divisions in each organism passes 
over into the body of the other. 



An Ascon Sponge. 



AN ASCON SPONGE 

{Leucosoknia sp.). 

General Anatomy. — Specimens of Leucosoknia may be 
abundantly found along the New England shores, attached 
to rocks, seaweed, and submerged wood-work near the low- 
tide mark. The specimens submitted for examination will 
be found to vary considerably in size and to not infrequently 
occur in little groups or clusters. ^ 

• Examine the specimens with a hand lens and note the fol- 
lowing : — 

Each sponge body is cylindrical and is attached by one end, 
the proximal, to some foreign support, while its /;r<? end 
presents a large opening, the " oscuhini'^ Press the sponge, 
and note that its wall is flexible. The larger sponges bear 
buds or branches. Do the buds or branches have oscula? 
Do the walls of the sponge becom.e in any way different as 
they approach the rim of the osculum ? 

Carefully lay open the sponge its entire length, cutting 
from the osculum to the base. The simple central cavity or 
cloacal chamber is thus exposed. Does the cloacal cham- 
ber communicate with the smaller cloacal chambers of the 
buds? 

Place one half of the sponge where it will quickly dry, and 
the other half, after washing it for a moment in water, place 
in alum or borax carmine, where it may remain from one to 

1 Specimens preserved in alcohol are more desirable for laboratory 
work than the living animals. 



6 Invertebrate Zoology. 

several hours. Utilize the time while the piece is drying, by 
drawing a cluster of the sponges (natural size, and also some- 
what enlarged), illustrating such characters as have been 
considered. 

Place the now dry piece of sponge upon a clean slide and 
examine the cloacal surface, using a low-power objective. 
The sponge appears to be made up of a multitude of needle- 
like bodies or spicules. The spicules are clearly of two 
kinds, radiate and linear. The radiate spicules form a some- 
what regular lattice, each spicule producing its three longer 
rays parallel to the wall of the cloacal chamber. A fourth 
and shorter ray extends, from the common point of origin 
of the three longer, perpendicularly into the cloacal chamber 
and, as the sponge now Hes, towards the eye of the observer, 
as may be demonstrated by the use of the fine adjustment. 
The linear or biradiate spicules are somewhat curved. Do 
they He in a plane mainly without or within the ^^ quadri- 
radiate spicules " ? 

Make drawings of the spicules, giving them their relative 
dimensions. 

Remove the specimen from the stain, wash it for a 
moment in water and then carry it through grades of alco- 
hol to absolute. Clear in clove-oil and mount in balsam, 
cloacal surface uppermost. (Do not allow the cover-glass 
to rest too heavily upon the specimen.) Examine under 
compound microscope. 

The spicules will now be found to lie below (outside of) 
a layer of small cells, the endoderm^ the nuclei of which are 
clearly defined. The endoderm entirely covers the inner 
surface of the cloacal chamber, and its cells, during life, are 
provided with, flagella and '* collars,"" the activity of the for- 
mer producing a current of water, which enters the chamber 



An Ascon Sponge. 7 

through numerous pores and leaves through the osculum. 
The pores are easily determined, in the preparation under 
consideration, as small round openings free from nuclei and 
surrounded by the rays of the spicules. 

Outside the endoderm (below in the present specimen), 
and surrounding the spicules, are the 77iesodertn cells. The 
mesoderm cells are not arranged as a single layer, but occur 
irregularly through the mass of spicules. Their nuclei are 
often seen as granular bodies along the rays of the spicules, 
and their protoplasm appears as a faintly stained reticulum. 
While the endoderm cells have a definite outline, the meso- 
derm cells are irregular and vuillipolar. The spicular skele- 
ton is formed by the activity of the mesoderm cells. 

Still a third layer of cells, the ectoderm, has been described. 
Its cells form a very thin tissue, easily destroyed, and too 
difficult of demonstration to be here considered. It covers 
the outer surface of the animal, and is probably somewhat 
soiled with foreign matter. 

Make a drawing illustrating the points above mentioned. 

Reproduction. — Many of the larger specimens prepared 
and mounted as above directed will be found to bear reproduc- 
tive cells. These cells appear as large, deeply stained bodies 
resting in the mesoderm and covered by the endoderm. 
They are of two kinds, the male and the female. The male 
cells or sperinatozoa occur in spheres, each sphere containing 
several hundred sperm-cells. The nuclei of the sperm-cells 
give to the surface of the sphere a peculiar dotted appear- 
ance, and are considerably smaller than the entodermal 
nuclei. The sperm-spheres, however, are large, their diame- 
ter being about one-third the length of a long ray of a 
quadriradiate spicule. 



8 Invertebrate Zoology, 

The ova or egg- cells ^ though often as large as the sperm- 
spheres, are provided with only a single large nucl^s. In 
this latter may rest a nucleolus. The egg-cells are often 
amoeboid in form. They are seldom spherical. 

Make drawings of ova and sperm-spheres. 

Segmenting eggs are not infrequently found. Such eggs 
often have a clear space around them and between their 
several segments or blastomeres. Two- and four-celled 
stages are most abundant. Are all the blastomeres provided 
with nuclei? Can you find an unsegmented ovum that has 
two nuclei? 

If a cluster of clean sponges be placed in two per cent 
chromic acid for a day and then carefully washed, stained, 
imbedded in celloidin and cut transversely, the arrangement 
of the cell- layers and the structure of the segmenting ova 
will be more clearly shown. The endoderm will be found 
to consist of closely appressed, somewhat columnar cells, 
forming a layer considerably thinner than the outer, less dis- 
tinct mesoderm. The delicate ectoderm will probably be 
destroyed. 

The spicules have been dissolved by the chromic acid, 
but the cells once surrounding them are now seen to be 
quite irregular in outline and to hold in their meshes the 
ova and the sperm-spheres. 

Make a drawing of the transverse section. 



A Syco7t Sponge. 



A SYCON SPONGE 

{^Grantia sp.). 

General Anatomy. — Simple sponges, which have been 
described under the name Gf'a7itia, are found associated 
with Leucosolenia along the Atlantic coast. Specimens vary 
considerably in size, the larger sometimes reaching one inch 
in length. 

Examine a dry specimen with a lens and note the general 
outline of the body, the somewhat expanded dase, the ter- 
minal oscidum^ surrounded by a funnel of spicules, and the 
numerous incicrrent p07'es, distributed over the external sur- 
face of the body, and more or less hidden by the numerous 
spicules. Are there bicds attached to the sponge body? 

Make a drawing illustrating the above points of the exter- 
nal anatomy. 

With a sharp scalpel open the sponge by making a longi- 
tudinal stroke from base to osculum. The central cavity or 
cloaca will be exposed, and its walls will be found pierced 
with numerous openings, the gastric ostia. Note that the 
cut edges, much thicker than in Leiccosolenia, are traversed 
by parallel tubes, those entering the central chamber through 
the gastric ostia being called radial canals, while the shorter, 
which enter from without through the incurrent pores, are 
called the iiicurrent canals. The incurrent canals commu- 
nicate with the radial canals through certain small openings 



lO Invertebrate Zoology. 

which cannot be seen at present. Do you find anything 
that might strain the water as it enters the incurrent canals ? 
Do the buds communicate freely with the cloaca of the. 
parent ? 

Examine with lowest power of compound microscope. 
The outer lighter-colored layer of the sponge is now seen 
to be made up of innumerable, needle-like spiades^ while 
the inner portion is supported by radiate spicules. 

Make enlarged drawings of the parts thus far considered. 

Cut a thin transverse section of a dry sponge and note 
the radial canals, and the smaller and also straight incurrent 
canals lying parallel with them. Are the needle-like spicules 
arranged more abundantly over the peripheral ends of the 
radial canals? Note the arrangement of the triradiate 
spicules in the walls of the tubes. T-shaped spicules are 
arranged around the cloacal chamber, each sending one ray 
into the cavity. Recall the spicules of the Ascon. Do any 
of the incurrent canals pass through the wall of the sponge 
from the periphery to the cloacal chamber? 

Make a drawing showing the arrangement of the spicules. 

Examine now a specimen that has been decalcified, stained 
and cut into transverse sections by means of a microtome. 
The spicules will not be present though their surrounding 
mesodermal cells will appear as a delicate nucleated retic- 
ulum extending between the parallel tubes and into pyram- 
idal masses at the peripheral ends of the radial canals. 
Endodermal cells, as a single layer, line the cloacal chamber 
and the radial canals ; but while the cells of the former are 
flattened out and form a "pavement epithelium," those of 
the radial canals retain the flagella and collars present in 
the Ascon, and by their activity induce the circulation of 
sea-water. Note that the incurrent canals are lined with 



A Sycoji Sponge, 1 1 

pavement epithelium, ectoderm, quite different from the 
lining cells of the radial tubes. ^ The incurrent pores through 
which the sea-water enters the radial tubes are small and 
somewhat difficult to demonstrate. They may frequently 
be found in section, as interruptions of the even course of 
the endodermal lining along the peripheral portion of the 
radial tubes. They are more easily determined as minute 
openings in such portions of the section as permit the exam- 
ination of the s2C7'face of the entoderm. 

Make a drawing of the cross-section just examined. 

Reproduction. — In the stained specimens there will fre- 
quently be found large amoeboid cells in the substance of 
the mesoderm. Such cells, as was the case in the Ascon, 
are the reproductive cells, male or female, and in a single 
sponge may occur in varying stages of development. The 
sperm-spheres and the segmenting ova are clearly covered 
by a layer of epithelial cells. The sexes are usually not 
united in the same sponge-individual. 

Draw one of the reproductive cells and show its nucleus 
and nucleolus. Draw also a sperm-sphere or a segmenting 
ovum, showing its position in the mesoderm and its epithelial 
covering. 

1 The difference in the lining of incurrent and radial canals is clearly 
seen in specimens that have been cut at right angles to the axes of 
these canals. While the endodermal tubes appear as circles of broad 
outline, the ectoderm of the incurrent canals forms a most delicate 
circle. 



12 Invertebrate Zoology, 



THE HYDRIFORM STAGE OF A CAMPA- 
NULARIAN HYDROID 

( Canipanularia sp.) . 

External Anatomy. — Examine with a low power and 
note the more or less branching hyd7'ocaulus or stem. It is 
supported upon a root-hke expansion or hydrorhiza. What 
is the order of the branching? Note any structures that 
may give flexibihty to the horny, tube -like covering or pe7d- 
sarc. Do you find the perisarc enlarging at its free extremi- 
ties into bell-shaped cups or hydrothecce? The hydrothecae 
give protection to the zooids or hydraiiths. Observe that 
certain of the hydrothecae may become considerably en- 
larged, forming gonangia. Each ripe gonangium may con- 
tain a number of medusa buds. 

Make an enlarged drawing, naming the several parts. 

Examine a single expanded hydranth under a higher 
power and note the position of the terminal mouth. The 
mouth is supported upon a proboscis or mamcbrium. Around 
the base of the manubrium are arranged the tentacles which, 
during life, are capable of considerable movement. Below 
the circle of tentacles, and quite enclosed by the hydrothecae, 
the body of the hydranth is to be noted. What is the 
arrangement of the tentacles in a contracted zooid or 
hydranth ? 

Use a still higher power. Do you find certain wart-like 



Campaniilaria7i Hydroid. 13 

batteries of nematocysts or '' lasso-cells'' at varying positions 
along the tentacles? In the living specimens (or in a living 
Hydra, held under a light cover- glass and treated with dilute 
acetic acid), note that each nematocyst has a rounded body, 
an elongated filament, and, at the base of the latter, a few re- 
curved spines. 

Make a drawing of an expanded and of a contracted 
hydranth. 

Internal Anatomy. — If a clean, living specimen is 
selected there will be Httle difficulty, by focussing through 
the transparent perisarc, in making out the internal anatomy. 
If alcoholic specimens are used, portions of the colony should 
be stained, cleared, and mounted as described in the Appen- 
dix. Observe that the perisarc of the hydrocaulus contains 
a fleshy axis or coenosarc. The coenosarc is made up of 
three layers, and encloses, as a tube, the centrally lying 
coelenteric or ''body-cavity'' Of the three layers the ectoderm 
is the most external. It is made up of transparent, nucleated 
cells, and is separated from the innermost and more granular 
e7idoder?n by a very delicate, third, transparent, stipporting 
layer. 

If the specimen is still alive, note the circulation of the fluid 
in the body-cavity. How is the circulation brought about? 

Examine one of the tentacles and determine the just de- 
scribed layers. To which layer are the nematocysts con- 
fined? The body-cavity does not extend into the tentacles. 
Demonstrate, if you can, the presence of the three layers in 
the body-wall of the hydranth. Is the cavity of the hydranth 
in direct communication with the cavity of the hydrocaulus ? 

Make a drawing of the stem, of a tentacle, and of a 
hydranth, illustrating the three layers. 



14 Invertebrate Zoology, 

The Digestive System. — Nutritive material entering 
the mouth is reduced to a semi-fluid condition, and, by 
the action of the endodermal cilia lining the body-cavity 
of the hydranth and hydrocaulus, is carried to the various 
portions of the colony, where it is appropriated and digested 
by the individual endodermal cells. 

The Circulatory System is not specially differentiated 
from the digestive system. 

The Muscular System. — At certain points in the ten- 
tacles of favorable specimens, elongated '^ muscle fibres " 
have been described. They lie on the outer surface of the 
supporting layer. 

The Nervous System. — In the present stage of the 
Hydroid a nervous system has not been found. 

The Reproductive System. — The fertihzed ovum of a 
Hydrozoan ordinarily develops into a colony of zooids. 
Such a colony we have just been considering. Through a 
process of branching, new colonies are asexually produced, 
and from the colonies medusa-buds are also produced. 
A brief search will probably reveal the presence of several 
gonangia or specialized hydranths. Each gonangium, some- 
what larger than a hydranth, contains a fleshy central axis or 
blastostyle, which is morphologically equivalent to the body 
of a hydranth. The blastostyle is produced distally into 
a manubrium. Is there a mouth? Are there tentacles? 
Do you find the same layers that were present in the 
hydranth? Is there a central body-cavity? Along the side 
of the blastostyle are medusa-buds, in varying stages of de- 
velopment. Which are larger, the terminal or those nearer 
the base ? How many are there ? 

Draw a gonangium with its contents. 



Campantdarian Hydroid. 15 



THE MEDUSOID STAGE OF A CAMPANU- 
LARIAN HYDROID. 

General Anatomy. — The medusa-buds were observed 
to be produced asexually along the sides of a speciaHzed 
hydranth, the blastostyle. If some of the older buds are 
examined, they will be found to be shaped Hke an umbrella. 
The concavity of the umbrella is turned towards the exterior, 
and the margin is provided with numerous mai'ginal ten- 
tacles. Stretched across the opening of the umbrella, as a 
perforate diaphragm, is the so-called velum. The presence 
of a velum is characteristic of the Hydromedusae and gives 
to them the name Craspedota. 

By the convex surface the medusa-buds are held to the 
blastostyle, through which, for a time, they receive their 
nourishment. When finally mature, the buds break away, 
and, passing through a terminal opening in the gonangium, 
reach the sea-water as free-swimming medusae.-^ 



If possible, examine a living medusa and note its peculiar 
movements. How many tentacles are there along the mar- 
gin of the disc? Do you note a centrally projecting tube, 
the manubrium? At its free end the mouth is situated. 

1 The terms exufnbrella and subujnbrella designate the aboral and 
oral portions respectively. The attachment of the blastostyle is at the 
aboral or exumbrella portion, while the concavity, surromided by the 
marginal tentacles, is formed by the subumbrella portion. 



1 6 Invertebrate Zoology. 

Can you trace an opening leading from the mouth into 
a central cavity? There are radiating chymiferous tubes 
leading from the base of the cavity of the manubrium to the 
periphery of the disc, where they open into the very delicate, 
circular, circicmferential canal} Is the arrangement of the 
chymiferous tubes and the marginal tentacles correlative? 

The Sexual Reproductive Organs lie one on each radiating 
chymiferous tube, and appear, when viewed from below, as 
wart-Hke projections. Their contents, as eggs or spermatozoa, 
are dehisced into the sea-water. 

The Nervous System and Sensory Organs. — A circu- 
lar nervous tract consisting of a plexus of nerve cells extends 
entirely around the margin of the umbrella. Fibrillae extend 
from the edge of this ^*ring" to muscle fibres and to certain 
marginal sense-organs. The latter may be tactile, "' audi- 
tory " or visual The tentacles are the principal tactile 
organs. The so-called " auditory vesicles " are probably 
organs of equilibration, and medusae being thus provided are 
called vesiculate, while those having pigmented visual spots 
are called ocellate. The visual spots are more frequently 
found at the bases of the perradial tentacles. 

Make drawings that will show the important points in the 
anatomy of the Hydromedusa. 

1 The chymiferous tubes are more frequently four in number and 
determine four radii {perradii^ of the umbrella. In certain Campanu- 
larians, however, there are eight or more of these radiating tubes. 



Tnbulariaii Hydro id. 17 



THE HYDRIFORM STAGE OF A TUBULA- 
RIAN HYDROID 

{^Peiinaj'ia tiarella). 

External Anatomy. — Examine with a low power, and 
note how the present specimen differs from the Campanula- 
rian in its order of branching, in the disposition of its 
hydrorhiza, and in the termination of the branches of the 
hydrocaulus. No hydrothecae are present. How do the 
zooids or hydranths differ from those of the Campanularian ? 
Specialized gonangia are not present, but medusa-buds will 
be found as globular swellings along the sides of certain 
hydranths.^ 

IMake an enlarged drawing, naming the several parts. 

Examine a single expanded hydranth under a higher 
power, and locate the manubrium, the terminal mouth, the 
somewhat irregularly placed ^' shorter tentacles," and the 
whorl of '' longer tentacles " arranged around the base. Is 
the number of tentacles constant in different hydranths? 
Are batteries of nematocysts present? 

IMake an enlarged dra\\dng of a hydranth. 

Internal Anatomy. — Does the internal anatomy essen- 
tially differ from that of the Campanularian? Do you find 

1 Hydroids that are thus unprodded with hydrotheCcX and gonan- 
gia are united in the group Gymnoblastca^ while the Campanularian 
Hydroids (provided with hydrothecae and gonangia) are united in the 
group Calyptohlastea. 



1 8 . Invertebrate Zoology, 

ectodermal, endodermal, and supporting layers? Does the 
body-cavity extend into the tentacles ? 

Illustrate the internal anatomy by diagram. 

The Digestive, Circulatory, Muscular, and Nervous 
Systems are not essentially different from the same of the 
Campanularian. 

The Reproductive System. — As in the Campanularian, 
reproduction may be asexual (branching and budding) or it 
may be sexual. 

Though, as already noted, gonangia are not produced, 
medusa-buds are abundantly found attached, as was the case 
in the previously examined specimen, to the body or manu- 
brium of the hydranths. An examination of medusa-buds 
in varying stages of development will show that they arise 
as simple outpushings, or evaginations, of the body-wall. 
The more mature buds (about one-sixteenth of an inch in 
diameter) have all the essential characters of the same of 
the Campanularian, though the umbrella is here strongly 
four-ribbed and considerably elongated. The chymiferous 
tubes are four in number, and lead from the cavity of the 
manubrium. The velum has but a small opening leading 
into the cavity of the umbrella, and the marginal sense-organs 
are visual (ocellate). Either eggs or spermatozoa are devel- 
oped from the wall of the manubrium and are often in such 
quantity as to distort the medusa. One or two of the eggs 
are frequently much larger than the others, and may be 
thrown off before the medusa-bud breaks away from the 
hydranth. 

Make a drawing of a mature medusa-bud. 



An Actinian. 19 



AN ACTINIAN 
{Metridium margi7iatiim) . 

External Anatomy. — Observe in the expanded animal 
that the body is made up of a cyHndrical column, terminated 
above by a more or less flattened disc and resting below 
upon an irregularly shaped base. The column is pierced 
with small pores, ci7iclides, and is limited above by a ring- 
like fold, which contains a maj-ginal sphijicter or ring-muscle. 
The disc is capable of considerable expansion, and may 
present a regular number of lobes. It bears numerous rows 
of contractile tentacles, the older and larger of which form 
the innermost circles. These tentacles are simple outpush- 
ings of the substance of the disc. In the centre of the disc 
is the elongated fnouth or stomodceal opening, the lateral 
lips of which often rest against each other, and may even be 
united, while the terminal angles are somewhat thickened 
and form the siphonoglyphes, (In certain specimens but a 
single siphonoglyphe is present.) The elevated area imme- 
diately surrounding the mouth is the peristome. The base, 
or area of attachment, is an adhesive organ, expanded later- 
ally into a limbus, and capable of producing a considerable 
amount of motion. In the living animal the internal struc- 
ture is often to be seen through the transparent walls. 

Make a drawing of the specimen as seen from the side, 
and also as seen from above. 



20 Invertebrate Zoology, 

If the living animal is irritated, the tentacles are with- 
drawn, the disc is lowered, and by the contraction of the 
ring-muscle, the walls of the column are drawn together 
over the free end. If the contraction goes still further, 
numerous white, thread-like bodies, acontia, are seen to 
ooze from the cinclides. 

Make a drawing of the contracted animal. 

Internal Anatomy. — With a sharp knife divide the 
animal from disc to base, through a plane at right angles 
to the stomodaeal opening, and then remove from one of the 
halves the thin tissue of the base. The mouth will be 
found to lead into an elongated, thick-walled, and more or 
less wrinkled tube, the oesophagus. Is its wall in any way 
differentiated at the siphonoglyphes ? Below, the oesopha- 
gus opens directly into the coelenteric chambery a general 
cavity limited externally by the walls of the column and 
divided, or partially divided, into numerous smaller cham- 
bers by delicate, radially arranged partitions, the mesenteries 
or septa. Only six pair of mesenteries extend entirely across 
the coelenteric chamber and unite with the oesophagus. 
They are called the primary mesenteries, and are definitely 
arranged. Two pair of primary mesenteries, the di^rctive 
septa, occupy the plane of the longer axis of the mouth, 
and are attached to the walls of the siphonoglyphe. They 
divide the animal into two lateral halves. Between each 
pair of primary mesenteries — indeed, between any pair of 
mesenteries — is a limited chamber, the intra-radial cham- 
ber, while between two pair of mesenteries are the i^iter- 
radial chambers. There are six primary inter-radial 
chambers, three on either side. Between the primary 
septa are the secondary and tertiary septa, partially divid- 



All Actinian, 21 

ing the primary chamber into smaller secondary and ter- 
tiary chambers. 

Excretory and Respiratory System. — The waste pro- 
ducts of digestion are ejected through the opening of the 
mouth. Certain mesenterial filaments may (?), however, 
perform excretory and respiratory functions. These fila- 
ments are arranged along the free edges of the mesenteries, 
at the upper part appearing as an undulating Hne, while lower 
down each filament is coiled into a tangle of considerable 
size. Lying near the base of the mesenteries, in the deeper 
part of the coelenteric chamber, are greatly elongated mes- 
enterial filaments, the coiled acontia. 

The Reproductive Organs he near the free edges of the 
mesenteries on each side of the mesenterial filaments. . Each 
gland is a somewhat convoluted structure that dehisces its 
contents, eggs or spermatozoa^ into the coelenteric cavity. 
Are mesenterial filaments, acontia and sexual organs present 
on the primary septa? 

The Muscular System. — Though muscle fibres are pres- 
ent in the walls of the column, around the disc and around 
the mouth, the most characteristic muscles are developed 
along the septa, w^here they run vertically as longitudinal 
retractors. Are they on the inter- or intra-septal wall ? Does 
the arrangement on the primary mesenteries differ from the 
arrangement elsewhere ? ^ 

The Digestive and Circulatory System. — The sea- 
water freely mixes with the products of digestion, and the 

1 The tentacular retractors are arranged on the inter-septal walls of 
the directive septa; on the other septa they are on the intra-septal 
walls. 



22 Invertebrate Zoology, 

resultant nutritive fluid is carried, by the action of cilia, to 
all parts of coelenteric cavity. At the upper portion of 
each mesentery circular openings are to be found, placing 
the contiguous chambers in communication, and thus allow- 
ing free circulation. These openings, the septal stomata, 
form imaginary rings around the upper end of the oesopha- 
gus, and are possibly comparable with the circumferential 
canal of the Hydromedusa.^ 

Make drawings that will illustrate the more important 
points in the internal anatomy. 

1 The inner septal stojuata are placed just below the peristome near 
the oesophagus and pierce only the primary septa. The outer septal 
stomata are near the outer-wall and pierce all. the septa. 



The Mediisoid Stage of a Scyphozoan. 23 



THE MEDUSOID STAGE OF A SCYPHO- 
ZOAN 

{^Cyanea a?'ctica). 

External Anatomy. — In many points of its general 
anatomy the present form agrees with the medusa of the 
Campanularian Hydroid. A rounded aboral, abactinal^ or 
exiimbrella surface is distinguishable from an oral, actinal, 
or sicbu77ib7'ena surface. The former is generally convex, 
while the latter is more often concave. The margin is 
divided into eight large lobes. 

The month will be found in the center of the subumbrella, 
but surrounded and probably hidden by a mass of delicate 
fringe-like tissue, which, in life, may hang from the lower 
surface of the animal in four pleated folds. These folds, 
which are known as the oral tentacles^ are capable of con- 
siderable extension and contraction, and direct the food to 
the mouth. 

The oral tentacles may now be cut away, leaving only 
their line of attachment along the margin of the oral open- 
ing or mouth. This opening is elevated upon a short ma7itc- 
b7'iu??i, and has four radiating angles which determine four 
main radii of the animal, the so-called /<?;7'^^//. The four 
radii that might be drawn between the perradii are known 
as i7ite7'radii. The perradii and interradii extended to the 
margin pass directly through eight '' 77iargi7ial se7ise-07'gans,'' 



24 Invertebrate Zoology. 

tentaculocysts, or rhopalia. Each sense-organ is borne in a 
median sinus of one of the eight large lobes, — four perradial, 
and four interradial. 

Y oy\x perradial pillars are now to be observed as supports 
of the angles of the mouth. They are arranged radially, and 
at their proximal ends rest against the circular muscle of the 
subumbrella. This muscle is a broad, flat band of parallel 
fibres extending as a circle midway between the mouth and 
the margin. A pair of radial fmiscles extend into each of 
the eight lobes from near the peripheral edge of the circular 
muscle. There are, then, sixteen radial muscles, — four 
pairs of perradial and four pairs of interradial. 

Between each pair of contiguous perradial and interradial 
muscles {adradially) a collection of highly contractile te?i- 
tacles will be noted. These tentacles take their origin from 
near the peripheral edge of the circular muscle, and, during 
life, may be extended to an enormous degree. They are 
richly supplied with nemaiocysts and are the more essential 
prehensile organs. 

The sexual glands (ovaries or testes^ are four large lobu- 
lated organs located interradially and separated from each 
other by the perradial pillars. 

The velum, characteristic of the Hydromedusse, is not 
generally present in the Scyphozoa, and the term Acraspeda 
has hence been apphed to the members of this group in dis- 
tinction to the term Craspedota as defined for the Campanu- 
larian medusoid. 

Digestive System. — If a blunt probe is passed through 
the oral opening, the oesophagus will be found to be short, 
and, in cross-section, quadrangular. The openings into the 
four spacious interradial reproductive sacs lead from the 



The Medttsoid Stage of a ScypJiozoa7i. 25 

enlarged gastric cavity^ the peripheral boundary of which 
extends as far as the circular muscle. Four clusters of ten- 
tacle-hke interradial gastral filaments, or phacelli, are to be 
found encircling the deeper portion of the short oesophagus. 
They mark the dividing line between the oesophagus and 
the true gastric cavity. It is from the latter cavity, imme- 
diately within the phacelli, that the reproductive sacs take 
their origin. 

In injected specimens the chymiferoics tubes or gastro- 
canals can be followed, in their ramifications, through the 
substance of the disc and into the marginal lobes. Four 
main canals extend perradially and four interradially, finally 
opening into enlarged terminal cavities, located between the 
radial muscle bands and below and around the marginal 
sense-organs. 

Alternating with the pe7^radial and ifito'vadial canals are 
eight adj'adial canals which expand into as many terminal 
chambers, one above each cluster of tentacles. The central 
cavity of each tentacle communicates with the terminal 
adradial chamber. 

The Nervous System. — Near the base of each mar- 
ginal sense-organ ganglia have been found, though a mar- 
ginal nerve-ring has not been discovered. 



26 Invertebrate Zoology. 



A CTENOPHORAN 

{Mnemiopsis leidyi). 

External Anatomy. — The elongated gelatinous body 
will be observed to have a broader, two-lobed oral pole and 
a narrower aboral pole. From the latter eight series of 
combs, ctenophoral rows, or swimming plates extend meri- 
dionally towards the broader end, the two lobes of which 
{terminal lobes) may be folded together and cover certain 
structures. The 7nouth is a slit-hke opening which extends 
from lobe to lobe, its major axis thus determining the first 
perradius, and the plane {sagittal or ?nedian plane) passing 
through it and the axis of the body would divide the animal 
into symmetrical lateral halves. 

A pair of small papilli-form organs will be noted, one on 
either side of the mouth. These are the tentacular lobes, 
and a plane passing through them and the axis of the body 
at right angles to the sagittal plane, would divide the animal 
into an anterior and a posterior half, the one an exact coun- 
terpart of the other. Such a plane may then be called the 
transverse or lateral plane. It Hes in the second perradius. 

The true tentacles are considerably reduced. Each ap- 
pears as a small opaque spot, lying in a small pocket, midway 
between the lateral ctenophorial rows and a little aboral to 
the tentacular lobe. 

The ctenophoral rows are of different lengths. The four 
longer lie near the sagittal plane and extend over the ter- 



A Ctenophoran. 27 

minal lobes, and maybe called the terminal plates, while the 
four shorter lie nearer the transverse plane, and may be 
called the lateral plates. 

As the eight ctenophoral rows approach the aboral pole, 
each terminal pair become united at the margin of an aboral 
crater-like depression, and form a single line which passes 
down the wall of the depression in the plane of the first per- 
radius. The four lateral 7'ows, however, preserve their indi- 
viduality until they have reached the deeper portion of the 
depression. 

At the base of the depression is a small opaque spot, the 
" sensory body,'''' 

If each lateral ctenophoral row is followed orally, it will 
be found, at its lower end, to change its character somewhat 
abruptly. At this point, four long finger-shaped processes 
will be noted which extend freely between the terminal 
lobes. These processes are the '^ auricles''' and they lie 
interradially. Each auricle is somewhat flattened, its two 
richly ciliated edges being directed one away from and one 
towards the terminal lobe. The cilia of the first-mentioned 
edge continue, orally, the line of the true ctenophoral row. 
This continuation extends from the free end of the auricle 
aborally along the edge that is turned towards the terminal 
lobe until it has reached a point near the ^^ sensory body" 
midway between the neighboring terminal and lateral rows. 
At this point it unites with a much larger fringe that has 
extended aborally along the inner surface of each terminal 
lobe from near the sagittal end of the mouth. There are 
four of these large fringes. 

Internal Anatomy, — The opening of the mouth has 
been already observed. It leads into an oesophagus, which 



28 Invertebrate Zoology, 

is laterally compressed often to such an extent that its walls 
are actually in contact. A double plate is thus formed 
which hes in the median plane (perradially) . The flattened 
oesophagus opens near the aboral pole into a much smaller 
stomach. 

The thick layer of jelly-like tissue that lies between the 
walls of the oesophagus and stomach and the external integ- 
ument is traversed by certain gastro-canals, which, as diver- 
ticula, radiate from the stomach. 

If a living animal has coloring matter forcibly injected 
into the opening of the mouth, the course of these canals 
will be beautifully demonstrated. 

There are eight large gastro-canals that take their origin 
from the stomach, of which four arise laterally and in the 
second perradial plane and four arise interradially. A single 
pair of very small canals extend aborally in the first per- 
radial plane from the stomach to the region of the '^ sensory 
body." 

Of the four lateral canals, one pair, the more external 
{tentacular vessels)^ extend directly to the tentacles, while 
the other, deeper pair, run along the wall of the oesophagus 
as the oesophageal or gastric vessels. Each of the four inter- 
radial canals branches dichotomously soon after leaving the 
stomach. Eight meiHdional vessels are thus formed which 
lie under and parallel to each ctenophoral row. 

It is on the walls of the meridional vessels that the eggs 
and spermatozoa are developed. These reach the sea-water 
after passing through the stomach and oesophagus. 



The Starfish. 29 



THE STARFISH 

{Asterias sp.). 

External Anatomy. — Note the small, cylindrical bod}\ 
the radiating arms^ the centrally placed mouthy and the 
red inadreporic plate. A vertical plane passing through 
the madreporic plate and thence across the body and along 
the median line of the opposite arm will divide the animal 
into a right and a left half. There is then bilateral sym- 
metry. 

Do you find specialized spines surrounding the mouth? 
How many? Are the spines specially developed on other 
portions of the animal ? Note the ambidacral ficrrows, 
grooves, which extend along the 07'al surface of each arm. 
Each groove is filled with two zigzag rows of ambulaci-al 
suckers. Do you find any structure on the aboral side of 
the arms that suggests a median radial hne? Find the 
pedicellarice^ minute pincer-like organs around the bases 
of the aboral spines. On what other portions of the animal 
are they present ? 

Draw the animal as seen from above, and again, as seen 
from below. 

With a strong pair of scissors remove the entire aboral 
surface of the animal and without in any way injuring the 
underlying ^^ soft-parts." 



30 Invertebrate Zoology, 

The Digestive System. — The mouth leads through a 
short cesophagus into a thin-walled stomach, the five lobes of 
which normally lie in the cavities of the five arms, though 
certain lobes, and indeed at times, while feeding, the entire 
stomach, may be completely everted through the mouth. 
Do you find the gastric retinae tors, bands of muscle which 
draw the lobes of the stomach into the cavities of the arms ? 
The lobulated digestive glands appear in each ray as a pair 
of voluminous masses of a Hght olive-color. Each gland 
unites with its fellow, centripetally, and opens, through a 
common pore, into the stomach. Note the suspending 
711 esen teric fold. 

Inflate the stomach by blowing into the oral opening. 
The organ will be found to lead, above, into a short cone- 
shaped intestine, which opens to the exterior through a 
minute pore, the anus. Leading from the left wall of the 
intestine is a somewhat branched organ, the respiratory 
tree. It is made up of two main divisions, separated by 
an interradius. The organ may perform an excretory 
function. 

The Reproductive System. — Though the testes and 
ovaries bear a superficial resemblance to each other, the 
sexes are separate. The sexual glands appear in mature 
specimens as a pair of light-colored, grape-like masses, 
extending from near the body out into each ray.^ Trace 
the ducts to their external openings. (The openings may 
be found well into the angles between the arms.) 

Draw the reproductive system. 

1 The testes are in living specimens of a whitish color, while the 
ovaries are pale yellow. 



The Starfish, 31 

The Water-vascular System should be studied in a 
specimen that has been artificially injected. The ambulacral 
suckers were noted above as a series of tube-like organs 
lying along the ambulacral furrows. Each sucker passes 
upward, aborally, through a pore, the ambulacral pore, and 
expands within the cavity of the arm, into an ambulacral 
vesicle or ampulla. The ampullae of each arm are in com- 
munication with a common radiating water-tube^ which lies 
in the median hne of each ray beneath the ridge of calcare- 
ous a7nbulac7^al ossicles. Follow the radial tube centripe- 
tally. It will be found to arise from a circum-oral ring. 
The Polian vesicles^ ten in number, are enlarged ampullae, 
arranged in a circle around the mouth. The racemose vesi- 
cles^ nine in number, have their axes lying at right angles to 
the Polian vesicles and extend horizontally into the cavity 
surrounding the oesophagus. At the place where the tenth 
vesicle might occur a rigid tube, the stone-canal, takes its 
origin. The stone-canal extends to the lower side of the 
madreporic plate. 

Make a drawing of the water-vascular system. 

The Circulatory System. — A delicate sac, the ''pericar- 
dium,''' will be found lying immediately posterior to and be- 
neath the stone-canal. Careful injecting will show that from 
this sac certain minute blood-vessels pass to varying parts of 
the body, following, in the main, the course already taken by 
the water-vascular system. 

The Nervous System. — Part the ambulacral suckers 
from the median line of each furrow, and note the deeply 
lying nerve-cord, the " radiating nerve.'"' It extends from a 
circum-oral nerve-ring to a red eye- spot. The latter occu- 
pies a position at the tip of the arm. 



32 Invertebrate Zoology. 

Draw the nervous system. 



With a strong knife, make a cross-section of one of the 
arms. Note the perivisceral cavity and identify the con- 
tained organs. Observe the arch of the aboral integument, 
and below, the large furrowed ambulaa^al ossicles. Where 
the ambulacral ossicle of the right meets that of the left, do 
you find the cross-section of the radiating ambulacral water- 
tube? 

Remove the aboral integument from one of the arms and 
note that the ambulacral plates form an unbroken ridge. 
Trace this ridge to the tip of the arm and draw it, some- 
what enlarged. 

Remove the aboral integument from the body, taking care 
not to disturb the madreporic plate. Clean the skeleton 
and note any local specializations of the ambulacral plates. 
Do you find inter-radial partitions ? 

Draw the skeleton of the body. 



A7t Echinoid, 33 



AN ECHINOID 
{Arbacia punctulatd) . 

External Anatomy. — Compare the oral and aboral 
surfaces with the same of the starfish. Note that there are 
five ambulacral areas, separated by five inter-ambidacral 
areas. Both areas bear numerous regularly arranged spines. 
Note the "ball and socket" joint that permits movement 
of the spines. Are all the spines, of different parts of the 
body, of the same general structure ? Where are they most 
elongated ? 

The aboral region is centrally free from spines, and is 
called the pe7Hp7'oct, in contradistinction from the mem- 
branous tract around the mouth, the peristome. Find ten 
large ambulacral suckers on the peristome. Are pedicel- 
laricB to be found on the peristome ? On other portions of 
the body ? How do they differ from the same organs of the 
starfish? The periproct will be found to be perforated at its 
centre by the opening of the amis which is covered by 
four triangular valves. 

Forming the periphery of the periproct, are five radiating 
plates, the genital plates. Each genital plate will be found 
to form the apex of the inter-a^nbulacral sejdes, and to be 
perforated by a small opening leading from the sexual glands. 
One of the genital plates will be found to be larger than its 
fellows and to appear more or less granular. It is the 



34 Invertebrate Zoology. 

madreporic plate, and is directly comparable with the same 
of the starfish. Arranged between the genital plates, and 
consequently at the apex of the ambulacral areas, are the 
five small ocular plates. 

Make drawings of the animal as seen from above and from 
below, naming the parts ; also make enlarged drawings of a 
spine with its '' ball and socket " joint and of a pedicellaria. 

Remove the spines and thoroughly wash the shell. The 
ambulacral and inter-ambulacral areas will be clearly shown. 
Find the openings through which the ambulacral suckers 
may be thrust out. What is the arrangement of these open- 
ings, the ambulacral pores ? 

Make a drawing of the denuded shell. 

The Digestive System. — Around the margin of the 
mouth the five hard teeth will be observed. With a pair 
of scissors carefully remove the membranous peristome and 
wash out the body-cavity with clean water. The oesophagus, 
after passing through the complicated dentary apparatus, 
inclines to the wall of the shell, where it passes into 
the somewhat enlarged and elongated stomach. Break- 
ing the shell if necessary, follow the course of the ali- 
mentary tract to the anus, noting any mesentery that may 
hold it in place, and observing the structure of its free 
border. 

By a diagram illustrate the course of the alimentary tract. 

The Reproductive System. — The sexes are separate, 
though, as in the starfish, the sexual glands superficially 
resemble each other. The glands appear as five radially 
arranged masses, and are closely attached to \k\^ perivisceral 
walls. Each gland opens to the exterior through the pore 
already noted in the genital plate. 



A7t Echinoid. 35 

Draw the reproductive system. 

The Water-vascular System. — A tube, the stone-canal, 
leads from the madi^epojHc plate to a circum-oral canal sur- 
rounding the oesophagus. From the circum-oral canal a 
radiating tube passes along each ambulacral tract, giving off 
branches to the several a?7ipullc6. The ampullae in turn 
supply the suckers, A so-called heart is to be found near 
the upper end of the stone-canal. 

The Nervous System. — A delicate nerve forming a 
circtnn-oral coinmissure surrounds the oesophagus inside the 
dentary apparatus. Nerves extend from it radially, along 
the inner surface of each ambulacral series, to the terminal 
ocular plates, where they end in the eye-spots. 

The Muscular System. — A number of minute muscle 
fibres will be found at the base of each spine, and a more or 
less complicated series is associated with the dentary appa- 
ratus. Find the protractors and retractor's of the dentary 
apparatus. The ifiter- alveolar muscles are arranged between 
the alveolar plates, which latter hold the teeth. 

Make drawings illustrating the arrangement of the muscles. 



36 Invertebrate Zoology, 



A HOLOTHURIAN 

{Thy one briareus). 

Note the general shape of the body\ the point of origin 
of the tentacles^ their number, and the oral and anal open- 
ings. The body is covered with papiUiform ambulacral 
suckers^ which, by careful observation, will be found to be 
arranged in five broad, meridionally disposed bands. On the 
upper side of the animal the suckers are less abundant than 
on the lower side. In the angle between the upper ten- 
tacles, the opening from the genital duct will be found. 
Examine the oral opening. Are there teeth? Are the ten 
large circum-oral ambulacral suckers of the sea-urchin rep- 
resented ? 

Make a drawing of the animal as seen from the side. 

With a pair of scissors open the animal longitudinally 
along the middle of the lower surface. Why is it not strictly 
correct to here speak of the '' ventral surface " ? 

The Digestive System is greatly elongated and extends 
as a coiled tube which partly fills the body-cavity. It is poorly 
suspended to the body-walls by a delicate '^mesentery," 
and in certain portions of its course becomes somewhat 
glandular. The mouth opens into an oesophagus which is 
surrounded by a cartilaginous structure that recalls the dentary 
apparatus of the urchin. The oesophagus soon enlarges into 



A Holothurian, Z7 

a thin-walled crop or stomachy from which the coiled in- 
testine takes its origin, and continues to its posterior open- 
ing into the cloaca. After making a careful drawing, remove 
the alimentary tract, cutting it just back of the stomach and 
anterior to the cloaca. 

The Respiratory and Excretory Systems. — Lying lat- 
erally in the body-cavity are the two main divisions of the 
many-branched respiratory tree. Each half of this organ 
will be found to open directly into the cloaca, through 
which it may receive fresh sea-water and become greatly 
distended. 

Make a drawing of the respiratory tree and the cloaca. 

The Reproductive System. — The ovaries and testes 
superficially resemble each other. The sexes are separate. 
The genital gland (ovary or testis) occupies a median 
position in the upper part of the body-cavity, and is made 
up of a multitude of delicate filaments which collectively 
form a brush. The organ is divided into a right and into 
a left half, and its duct leads directly to the opening already 
noted, between the two uppermost tentacles. 

Make a drawing of the reproductive system. 

The Water-vascular System. — In certain specimens 
the circum-oral water-tube or ring-canal will be found to sur- 
round the deeper portion of the oesophagus, and to give off 
one or two large and elongated Poliaii vesicles. Commu- 
nicating with the tentacles, the ring-canal gives them their 
power of expansion, and it also gives off five radiating canals, 
which extend over the body and supply the innumerable 
ambulacral suckers. Elongated filiform ampullce are abun- 
dant and hang from the inner surface of the body-wall. The 



38 Invertebrate Zoology, 

7nadreporic plate and stone- canal are much reduced. The 
former will be found, as a small calcareous sphere, in the for- 
ward part of the body. It communicates with the ring- canal 
by a slender tube {s tone- c anal) ^ lying below and parallel to 
the genital duct. 

Make a drawing of the water-vascular system, so far as 
you have been able to determine its course. 

Muscular System. — Note five meridional bands of 
muscles extending the entire length of the animal. Is the 
median band above or below? How are the retractors oj 
the tentacles and of the oesophagus arranged ? What is the 
arrangement around the cloaca ? The body- wall is tough- 
ened by the presence of many circular muscle fibres. How 
are they arranged ? 

Make a drawing that will illustrate the muscular arrange- 
ment of the fore and of the hind end of the body. 

The Nervous System is not easily dissected. There is 
a circum-oral nerve-ring, from which extend five radial 
divisions. 



A Ttirbellarian Worm, 39 



A TURBELLARIAN WORM 

{Bdelloura Candida or Bdelloura propinqica^. 

Two species of Bdelloura are abundantly found attached 
to the under surface and in the ^^ gill-books" of Limulus. 
The larger species {candidal may reach a length of 15 mm., 
while the smaller, often found aggregated in clusters on 
the cephalothoracic appendages, does not exceed a length 
of 8 mm. Certain internal characters also separate the 
species. 

External Anatomy. — The body is broad and flat, the 
anterior end elongated and pointed, the posterior wide 
and provided with a ventral sucker. The eyes are deeply 
pigmented, and the brownish intestine often gives a darker 
color to the middle region of the body. On the lower side 
the pi'oboscis hangs freely from near the middle of the 
animal, bearing at its extremity the mouth. In the living 
animal active cilia will be found especially abundant along 
the margin of the body. 

The Digestive System. — The opening of the mouth 
leads into the pharyngeal cavity^ contained in the proboscis, 
and from the proximal portion of the cavity the branching 
intestine takes its origin. 

The intestine should be examined in a specimen that 
has been compressed under a heavy cover-glass. It will 



40 Invertebrate Zoology, 

appear as a greatly lobulated organ, extending nearly from 
end to end of the animal, its lateral subdivisions giving 
a segmented appearance. It is built on the Tricladid 
type, one main branch or ramus extending anteriorly, and 
two extending posteriorly. Both anterior and posterior 
rami give off lateral lobes, the diverticula above mentioned, 
the rounded ends of which frequently becoming further 
subdivided. 

The Nervous System. — The pigmented eyes are sur- 
rounded in the living animal by a halo-like area, which 
marks the location of the brain. This organ consists of a 
pair of lobes, united across the median line by a commissure. 
From the brain certain sensory nejves extend anteriorly, as 
transparent lines, while extending posteriorly, as transparent 
bands, are the longitudinal nerve trunks, one on either side. 
Note that each longitudinal nerve trunk, after extending 
almost the full length of the animal, is united to its fellow 
of the opposite side by a broad posterior commissure. Other 
commissures will be found in certain favorable specimens 
to pass transversely across the animal, and to extend later- 
ally beyond the longitudinal trunks, nearly to the margins. 
These are the transverse com^nis suites, and their number 
is about the same as the number of pairs of intestinal 
diverticula. 

The Reproductive System. — The Turbellaria are 
mostly hemaphrodite. In the present species the ovaries 
are to be found in adult animals as a pair of rounded organs, 
located in the anterior portion of the body between the 
second and third or third and fourth intestinal diverticula. 
They are often more readily found if the mirror of the 
microscope is shielded by the hand, thus viewing the 



A Turbellarian IVonji. 4 1 

animal with reflected light. Frequently the oviducts may 
be traced as a pair of straight lines leading directly back- 
wards from the ovaries. The testes appear as rounded 
bodies, abundantly clustered along the margin near the 
ends of the intestinal diverticula, and in Bdellouj-a propinqua 
extending inwards between these lobes. The seminal ducts 
lead finally into elongated seminal vesicles, which extend 
posteriorly parallel to the sides of the pharynx, and finally 
curve towards the median line. They are quite easily 
found, being of an opaque gray color. The seminal vesicles, 
often filled with spermatozoa, open into a median pocket, 
the atrium, which in turn opens to the exterior from the 
oral or ventral side of the animal through a single pore. 
The ova are conveyed to this atrium through the oviducts, 
which are often difficult to follow. Lying lateral to the 
seminal vesicles, one on either side, are certain disc-shaped 
organs, somewhat larger than the ovaries, though often 
less distinct. The function of these organs is at present 
unknown. 

The Muscular System. — Both species oi Bdelloura are 
active swimmers, and the muscular system is especially de- 
veloped, though too difficult of demonstration to be now 
considered. 

Drawings should be made of the several systems. 



42 Invertebrate Zoology, 



A POLYCH^TOUS ANNELID 

{Nereis virens). 

External Anatomy. — The elongated body is terminated 
anteriorly by a triangular piece, the prostoiniutn^ which 
bears certain sense-organs^ and forms the most anterior part 
of the " head,^^ while the posterior end is terminated by a 
pair of flexible caudal cu-ri. Of how many segments or 
fnetameres does the body consist? What is the arrange- 
ment of the lateral appendages ? Note, through the trans- 
parent skin, the tnedian dorsal blood-vessel^ and on the lower 
side the median ventral ne^^ve-chain. The latter appears 
as a whitish line, extending almost the entire length of the 
animal, and presents enlargements, ganglia^ for each body- 
segment. 

The prostomium is borne on an enlarged ring, the peri- 
stomium or buccal somite. The tentacles are small and fusi- 
form ; and take their origin near the terminal point of the 
prostomium, from which they abruptly diverge. Immedi- 
ately lateral to and below the tentacles are the much larger 
and clearly segmented palps. In the furrow between the 
pro- and peristomium the cirri^ four on each side, take 
their origin. Are they segmented? The eyes or ocelli are 
somewhat difficult to find in alcohohc specimens. They are 
four in number, and are arranged in pairs on the dorsal sur- 
face of the prostomium. 



A Polychcetoics Annelid. 43 

The mouth will be found as a transverse fold of the 
integument of the antero-ventral surface of the peristomium. 

Make a drawing of the dorsal and of the ventral side of 
peristomium. 

Observe the varying size of the lateral appendages, espe- 
cially at the two ends of the animal. Carefully remove one 
of the larger bundles of lateral appendages and examine 
under a simple microscope. The bundle will divide itself 
into a dorsal and into a ventral parapodium. The former 
bears a large triangular blade, the gill. From the upper 
edge of the gill projects a small movable cirrus. Do you 
find ramifying blood-vessels in the gill? Do you find two 
fleshy lobes immediately beneath the gill? The dorsal lobe 
bears a large number of setce. 

The ventral parapodium is divided in much the same way 
as the dorsal. Do you find a ventral cirrus ? Ventral setae ? 
Closer examination will reveal the presence in each para- 
podium of a supporting chitinous rod, aciculum. 

Draw, naming the parts. 

Examine the posterior end of the animal and note how 
the lateral appendages become reduced. Which elements 
are first lost? What is the point of attachment of the ter- 
minal filaments ? Does the anus open dorsally or ventrally ? 

The external openings of the segnie7ital organs will be found 
on the ventral side of each body-segment, near the bases of 
the parapodia.^ 

In a specimen that has been killed with extended probos- 
cis note the large, laterally opening jaws, 

1 These openings are often difficult to find. They are placed at the 
summit of the rounded elevation that lies just medially of each ventral 
cirrus. The segmental organs themselves are often to be seen through 
the transparent integument of smaller specimens. They are opaque 
white in color, and lie just lateral to the longitudinal muscle bands. 



44 Invertebrate Zoology, 

Draw. 



Open the animal along the mid-dorsal line, and, after 
gently pinning the cut edges apart, note the regular seg- 
mentation of the body-cavity. The transverse partitions or 
dissepime7its correspond in position to the constrictions 
between the successive rings or metameres. 

The Digestive System. — Cutting through the dissepi- 
ments, partially reflex the body-walls from the alimentary 
canal. The mouth will be found to lead into a protrusi- 
h\e pharynx which, in turn, leads into a somewhat smaller 
and less muscular crop. The crop, separated from the 
pharynx by a marked constriction, is in turn separated in 
the same way from the elongated and thin-walled stomach- 
intestine. The latter extends the remaining length of the 
animal. Do you find muscles connecting the pharynx to the 
inner walls of the peristomium ? 

These muscles are the ^^ protractor's y Their points of 
origin and insertion should be clearly established. The 
lesser protractors are also longitudinally arranged, but are 
not attached otherwise than to the walls of the pharynx. 
The 7^etractors, unless the pharynx is extended, will be ob- 
served as fine fibres in the region of the first and second 
metameres. Determine their distribution. 

The Crop. — Are there muscle fibres extending from the 
crop to the body- walls? Do you find di gland on each side 
of the crop? Trace its duct. How do the walls of the 
crop compare with those of the pharynx? 

The Stomach-Intestine. — Is this portion of the ali- 
mentary tract regularly constricted throughout its entire 



A PolycJicetoics Aimelid, 45 

length? Do the constrictions invariably correspond to the 
surrounding body-rings? Are there any local changes in 
the texture or color of the stomach-intestine that might 
argue changes in function? Do you find a ventral mesen- 
tery attaching the tube to the mid-ventral line ? (The dor- 
sal mesentery has probably been destroyed in opening the 
animal.) 

Make a drawing of the dorsal view of the alimentary 
tract, naming the parts. 

With a pair of sharp scissors open pharynx, crop and in- 
testine, along the mid-dorsal line. The interior of the 
pharynx will be found to present an anterior, tooth-bearing 
and a posterior, undifferentiated portion. Note the internal 
lining of the crop, and the small opening leading from it to 
the much thinner-walled stomach-intestine. Is the lining 
membrane of the latter different from that of the crop ? 

The Circulatory System in Nereis consists of a closed 
system of tubes in which the blood, holding in suspension 
numerous red blood-cells, circulates. The median ventral 
blood-vessel extends nearly the entire length of the animal. 
It Kes ventrally to the ahmentary tract and sends out lateral 
branches to each segment of the body. These lateral 
blood-vessels ramify through the gills and over the organs, 
uniting again, above, in a median dorsal blood-vesseL The 
latter rests upon the intestine. In the anterior portion 
of the animal, due to the presence of the complicated 
pharyngeal apparatus, the circulatory system is somewhat 
less regularly arranged. — The dorsal vessel is contractile, 
and forces the blood from the posterior towards the head. 



46 Invertebrate Zoology. 

The Muscular System. — How many distinct bands of 
muscle bundles are there? Their location? Are they seg- 
mented ? How are the muscles arranged around the acicula ? 

Make a drawing of the muscle bands of six segments, and 
give special attention to the acicula and their muscles. 

The Reproductive System. — The sexes are separate, 
and the reproductive glands periodically develop from the 
endothelium of the body-cavity. During the breeding 
season the eggs^ ox spermatozoa, often fill, as a granular or 
creamy mass, many of the chambers of the body-cavity. 
The eggs are fertilized after extrusion. 

The Excretory System. — The external openings of 
the segmental organs or nephridia have already been noted. 
By gently displacing the lateral edge of a ventral muscle 
band, a series of small flask-shaped bodies will be exposed, 
lying somewhat below the ventral acicula. They are the 
nephridia. Trace the nephridia anteriorly and posteriorly, 
and see if they are present in each segment. 

Make an enlarged drawing of one of the segmental organs. 

Nervous System. — Find the ventral chain of ganglia. 
Do the ganglia of the several segments occupy the same 
relative position? Can you find nerves leading from them 
to the organs or to the body- walls ? Is there anything to 
show that the ventral chain was originally double? Im- 
mediately back of the oesophagus, note the enlarged infra- 
cesophageal ganglion. Extending laterally and anteriorly 
from it are the oesophageal co7nmissures which unite above 
the oesophagus in the brain, or supra-cesophageal ganglion. 
Do you find nerves passing from the brain, or commissures, 
to the eyes, tentacles, or palps ? 

Make an enlarged drawing of the nervous system. 



A Polyzoan. 47 



A POLYZOAN 

{Bugula sp,). 

After a colony of this Polyzoan has remained in a solu- 
tion of caustic potash for a Httle time, all fleshy matter will 
be removed, and the skeleton may be washed in water and 
examined with a low power of the compound microscope. 

The skeleton is somewhat hardened by a deposit of hme, 
and is known as the coenoecium. It is made up of a multi- 
tude of little cups, zooecia^ which are arranged in double 
rows, back to back, each zooecium having its opening or 
" mouth " directed distally. The margin of the mouth is 
provided with one or two spines, and on one side a deep 
indentation or sinus will be found. This sinus is on the 
upper surface of the double row. For convenience, the 
side of the zooecium that is directed towards the median line 
of each double row may be called the inne7% the side 
directly opposite (lateral), the otcter, the side marked by 
the deep sinus, the upper, and the side opposite the sinus, 
the lower. The end of the zooecium which bears the 
"mouth" is the distal, and is directed towards the free 
growing point ; that directed towards the attachment of the 
double row is the pi'oxinial. It will be noted that the 
branching of the coenoecium is always dichotomous. 

On the outer margin of the sinus of the older zooecia, 



48 Invertebj^ate Zoology. 

"bird*s-head ^^ structures, or avicularia, will be found.^ Near 
the proximal ends of certain older zooecia, on the upper 
surface, spherical bodies will be found. They are egg-cap- 
sules, or ooecia, and have a diameter about equal to that of 
the zooecia. 

By focussing deeply into the distal portion of one of the 
zooecia, an irregular oval opening will be observed to lead 
from its inner side. This opening is the rosette or commu- 
nication plate and leads into the proximal end of the zooe- 
cium next above and on the opposite side of the double 
row. 

In an alcoholic specimen that has been properly killed 
and preserved, the walls of each zooecium will be found to 
extend distally and to be terminated by a circle of fourteen 
long tentacles^ the zooecium together with the fleshy parts 
being known as d, polypide. The knob-shaped body bearing 
the tentacles is the lophophore. It is pierced by the mouth 
opening, which is placed in the centre of the tentacular 
crown. In life, the cilia covering the tentacles whip the 
food into the mouth, the pharyngeal ciUa there carrying it 
still further into the digestive tube. The anal opening is to 
be found on the inner side of the lophophore just below the 
circle of tentacles. It is often more readily found if the 
zooecium be examined from the lower side. Make a drawing 
of a polypide. 

Digestive System. — The digestive tract is V-shaped. 
The pharynx leads into a stomach, which is provided with a 

1 The jaws of the avicularia, during life, are frequently closed upon 
small animals, the decaying bodies of which may attract smaller 
organisms upon which the Bugula feeds. 



A Polyzoan, 49 

proximally directed pouch, the coecum. The coecum forms 
the lower curve of the V. The intestine, richly ciliated, 
extends from the coecum to the rectu?n; the latter is often 
better seen on the lower side of the zooecium. A loose 
mass of non-muscular tissue, the funiculus, extends from 
the lower end' of the coecum to the deeper portion (prox- 
imal) of the zooecium. Make a diagram of the digestive 
tract. 

The Circulatory System. — Avascular circulatory sys- 
tem is not present in Polyzoa, though the fluid contained in 
the body-cavity bears numerous cellular corpuscles. It 
probably becomes purified in the thin-walled, hollow tenta- 
cles. 

The Muscular System. — During life the lophophore, 
together with the tentacles, is often forcibly retracted into 
the cavity of the zooecium. This contraction is brought 
about by the action of certain 7'e tractor muscles, which may 
be seen in favorable specimens extending across the body 
or coelomic cavity from the inner surface of the zooecium to 
the inner walls of the pharynx and lophophore. 

The Nervous System is represented by a supra-cesopha- 
geal ganglion, situated between the mouth and the anus. 
From it certain nerves go to the tentacles. There are no 
differentiated special sense-organs, and the entire system is 
too difficult of demonstration to be considered in the present 
course. 

The Reproductive System. — The increase in the num- 
ber of polypides in the colony, or zoariu7n, is brought about 
asexually by '' budding," though the more mature polypides 



50 Invertebrate Zoology. 

are provided with true sexual glands. The ova are often 
found in varying stages of growth lying in the body-cavity 
near the coecum. They are yellowish in color and oval 
in outUne. The spermatozoa lie deeper, near the proximal 
end of the funiculus and form a doudy mass. 



A Gephyrean Worm, 51 



A GEPHYREAN WORM 

(Phascolosoma gouldii) . 

External Anatomy. — The elongated body shows no 
external traces of segmentation, and lateral appendages 
are not present. The anterior end is often deeply with- 
drawn, though in specimens killed with considerable care 
the mouth will be found to occupy a terminal position, and 
to be surrounded by a crown of tentacles. The anal open- 
ing is not at the posterior end, but at the apex of a median 
papilla, situated near the middle of the animal, and marking 
the dorsal surface. 

Make a drawing of the animal as seen from the side. 

Internal Anatomy. — With a pair of scissors open the 
specimen along the median line a little to one side of the 
anus and pin the body-walls so as to expose the internal 
organs. Note the dorsal and the ventral pharyngeal retrac- 
tors. They are large muscle bundles, longitudinally arranged, 
and retract the anterior portion of the animal. 

The Digestive System. — Locate the mouth and follow 
the coiled stomach-intestine to the '^posterior" end of the 
body, thence back to its final opening on the dorsum. Do 
you find mesenteries ? Are there dissepiments ? 



52 Invertebrate Zoology, 

The Circulatory System is with difficulty followed out. 
There is a dorsal and a ve^itral vessel, much as in Nereis, 

The Muscular System. — What is the arrangement of 
the muscle fibres of the integument ? How many longitu- 
dinal bands are there? Examine again the pharyngeal 
retractors. 

Draw. 

The Reproductive System. — The sexes are separate. 
The sexual glands are situated near the base of the ventral 
pharyngeal retractors. The eggs or spennatozoa reach the 
exterior through the single pair of nephridia. Fertilization 
occurs after extrusion. 

The Excretory System. — The nephridia are a pair of 
large brown tubes which lie, somewhat freely, in the neigh- 
borhood of the retractors. Their openings to the exterior 
He a little in front of the origin of the dorsal retractors. 

Draw. 

The Nervous System. — The vent?^al cordlits along the 
mid-ventral line. Examine with a lens and see if it is pro- 
vided with ganglia. Do nerves leave the ventral cord? 
Find the oesophageal commissicres and trace them to the 
brain or supra- oesophageal ganglion. Are there pigmented 
eye-spots ? 

Draw. 



A Lamellibranch. 53 



A LAMELLIBRANCH 

(^Vefius mercenarid). 

External Anatomy. — The shell is composed of two 
bilateral halves or valves ; the hinge ^ or their common Hne 
of union, marking the dorsal side. The anterior end is 
less elongated than the posterior. The umbo is the dome- 
shaped elevation along the dorsal edge of each valve. Lying 
dorsally, between the valves, and extending posteriorly, is the 
ligament Which is the right valve, and which the left ? 
Note the parallel lines 0/ growth. 

Draw. 

Pry the shells apart and note the thickened mantle- 
edge, running parallel to the free margin of the shell. 
It is partly divided into a right and a left half, by lon- 
gitudinal openings. The anterior and ventral opening 
{pedal) gives opportunity for the protrusion of the foot 
while the posterior or siphonal permits the ingress and 
egress of salt water. 

Internal Anatomy. — Remove the left valve of the shell, 
taking care not to injure any of the underlying soft parts. If 
the animal has been killed by being allowed to stand in 
warm fresh water for a little time, the valves will naturally 
gape apart, and the attachments of the strong adductor 
muscles may be pressed from the shell with the handle of 



54 Invertebrate Zoology. 

the scalpel. Note the left mantle-lobe covering the whole 
surface of the animal, except the muscles. Through the 
semi-transparent mantle, the outlines of the underlying 
viscera may be seen. 

Along the dorsal edge, midway between the muscles, por- 
tions of the dark green liver, the cream-colored reproductive 
gland, and the brownish Kebe^^'s organ are to be noted, in 
the order named. Further posteriorly and dorsally, between 
Keber's organ and the posterior adductor muscle, the heart 
may be observed, lying in the delicate pericardial sac. If 
the animal is still alive, the pulsations of the organ may be 
noted. Immediately in front of the posterior adductor, and 
lying somewhat lateral to the heart, the yellowish organ of 
Bojanns is to be noted. 

The foot is a plough-shaped organ, pointed at its anterior 
end, and supported from the lower margin of the great, 
swollen, soft-bodied visceral mass. 

With a pair of scissors remove the left lobe of the mantle, 
cutting around the anterior and posterior adductors. The 
visceral mass nearly fills up the cavity between the two mantle- 
folds {mantle or pallia I chamber^ and is crossed on each side, 
diagonally, by two fringe-like gills. If the gills are followed 
anteriorly, they will be found to end near two small gill-like 
organs which lie just posterior to the anterior adductor. 
These organs, of which there are two on each side, are the 
palps. They He, one pair above, and one pair below, the 
mouth-opening. 

Examine the siphonal region. The mantle will here be 
found to be specialized in such a way as to form two pro- 
trusible tubes, of which the lower leads from without into 
the mantle chamber. 

Make a drawing of the above-mentioned organs. 



A Lamellibranch. 55 

The Muscular System. — The strong anterior and pos- 
terior adductor muscles have already been noted. Is there 
any difference in their relative size ? Can you discover the 
retractors of the foot, smaller muscles lying near the adduc= 
tors? The siphonal muscles lie around the base of the 
siphon. Note any lines of attachment on the inner surface 
of the removed valve that correspond to the muscles just 
mentioned. 

The Respiratory System. — Pass a probe into the 
lower siphonal canal (the incuri'ent canal) and note that 
the canal may convey water into the mantle chamber. Into 
this chamber^ which is also known as the iiifra-branchial 
chainber, the gills or hranchicE hang. Each gill is made up 
of two parallel plates of rods or bars. Study carefully the 
attachment of the two pairs of plates of each side to the 
mantle, without, and to the body- wall, within. 

Inject water into the upper siphonal opening and notice 
that it fills a certain chamber lying above each pair of gill- 
plates or lamellae. This chamber is the sicpra-branchial 
chamber^ and on each side, above the outer and inner gills, 
has an outer and an inner division. The outer subdivision 
may be exposed by cutting along the Hne of attachment of 
the outer lamella to the mantle. The inner sub-chamber 
may be exposed by turning back both gills and cutting along 
the line of attachment of the inner lamella of the inner gill 
with the body-wall.^ Look into these chambers and note 
the numerous openings of the 7uater-pores, tubes which lead 
from between the gill-lamella3. 

Carefully slit open a gill in such a way as to separate its 
lamellae and, floating one of the lamellae on a slide, exam- 
ine with a compound microscope. If the gill is still alive, a 

1 The inner lamella is only partially united to the body-wall. 



56 Invertebrate Zoology, 

most beautiful ciliary motion will be observed. Note the 
supporting bars and the openings through the gill-lamella 
for the passage of water. This passes from the infra- 
branchial chamber into the water-tubes between the lamel- 
lae, and thence into the supra-branchial chamber. The 
supra-branchial chambers of the right and of the left side 
open into a common cloaca^ below and behind the pos- 
terior adductor. From the cloaca the water reaches the 
exterior through the upper siphonal or excurrent canal. 

Make drawings of all the parts of the respiratory appa- 
ratus. The arrangement of the supra-branchial chambers 
may be well shown by imaginary cross-sections. 

The Circulatory System. — The location of the heart 
within the delicate pericardium has already been noted. The 
organ will be found to consist of a median and strong-walled 
ventricle into which opens, from each side, through an au- 
ricula-ventricular openings a thin, triangular-shaped auricle. 
The lower side of the auricle, corresponding to the base of the 
triangle, lies above the supra-branchial chamber and receives 
the purified blood from the gills. The rectum, or posterior 
portion of the intestine, passes through the ventricle. In- 
jected specimens will clearly show the course of the arteries 
as they pass anteriorly and posteriorly from the heart. The 
bulbus arteriosus will be noted on the posterior aorta as a 
large contractile sac. 

The Excretory System. — The kidney, or organ of 
Bojanus, has already been noted. Examine under the 
organ and near its anterior end. Two small openings will be 
found. The more posterior is the opening of the ureter, and 
leads from the kidney. It Hes inside ^ the second, the repro- 
ductive opening. If a hair is carefully passed into the open- 

1 Nearer the median plane. 



A LaniellibrancJi. 57 

ing of the ureter, and the outer wall of the kidney is then 
dissected away, the probe will be found to have reached 
what is called the '^ upper limb " of the kidney. This cavity 
is a comparatively smooth and thin-walled sac. It is con- 
tinuous with the ^' low 67' limb ^'^ which lies posteriorly, and is 
provided with more glandular walls. This lower limb finally 
communicates, through a funnel-shaped opening, with the 
cavity of the pericardium. The opening into the pericardial 
space is small and somewhat difficult to demonstrate. These 
renal organs are comparable to the nephridia of A^ereis, 
Make a careful drawing of the parts just studied. 

Reproductive System. —The reproductive gland {testis 
or ovary) is a somewhat delicate and voluminous organ, par- 
tially enfolding the coiled intestine. The opening of its duct 
has already been noted. 

The Nervous System. — The left cerebral ga^iglion will 
be found as a small body, about the size of a pin's head, 
lying just behind the upper portion of the anterior adductor. 
Find the short, transverse commissure that connects it with 
its fellow of the opposite side. The viscei^al ganglia lie on 
the lower surface of the posterior adductor. They are yel- 
lowish masses, from which numerous nerves radiate. A 
larger nerve may be followed from the left visceral to the 
left cerebral ganglion. It is the cerebro-visceral connective, 
and Ues for the most of its extent near the surface. The 
pedal ganglia lie side by side in the substance of the ante- 
rior portion of the foot, and just below the visceral mass. 
Cerebro-pedal connectives may be traced through the visceral 
mass from the pedal to the cerebral ganglia. 

Make a drawing of the nervous system. 



58 Invertebrate Zoology. 

The Digestive System. — The mouth, already noted, is 
provided with an upper and an under lip, two transverse 
folds that apparently connect the upper and the under 
palps. (The position of the mouth can be very clearly seen 
if the clam is carefully removed from its shell and pinned 
out under water.) The posterior portion of the alimentary 
tract passing through the ventricle has already been noted 
as the rectu7n. Follow the rectum in its further course over 
the posterior adductor to its final opening into the cloaca. 

To now trace out the course of the entire digestive tube 
considerable care must be exercised. — Carefully pick or 
cut away, piece by piece, the side of the visceral mass. The 
short oesophagus will be found to lead upward and back- 
ward into the sto7nach. The latter is an irregular sac situ- 
ated dorsally and anteriorly, and has, opening into it, the 
ducts from the digestive gland or liver. The liver almost 
entirely surrounds the stomach. 

The intestine is long and coiled. It begins at the poste- 
rior end of the stomach, passes to the lower posterior por- 
tion of the visceral mass, and then curves to the left and 
forward, soon to again bed itself deeply into the surrounding 
viscera and take on several convolutions. Finally the intes- 
tine passes upward, posterior to and nearly parallel with the 
first section until, at the level of the stomach, it bends 
sharply backward to pass through the ventricle of the heart. 
During a portion of its course the lumen of the intestine is 
partially filled by a fold, the typhlosole. The tract does not 
lie in a " body-cavity." 

During the dissection of the digestive tract a long gelati- 
nous cord has doubtless been noted. This is the crystalline 
style. Its function is not known. 

Make a drawing of the alimentary tract. 



A Cephalophoroiis Molhisk, 59 



A CEPHALOPHOROUS MOLLUSK 

(Sycotypics canaliciUatus) . 

External Anatomy. — Examine an animal enclosed 
within its shell and note the following points : — 

The shell, unlike that of the Lamellibranch, consists of but 
a single piece ( Univalve) . It is twisted towards the right, 
around a central axis, the columella, and makes several 
revolutions or whorls from its apex or spi?^, to its lower 
opening or '^ 7?iouthy The side of the mouth nearer the 
columella is called the internal lip, while the outer, thin, 
convex edge is the outer lip. Extending from the mouth 
downwards (away from the spire) is an elongated groove, 
the canaL The line of union between two whorls is called 
the suture. Lines of growth extend as parallel series, at 
right angles to the suture, and parallel to the edge of the 
outer lip. Frequently the shell is covered externally by a 
felt-like horny epidermis. 

Draw the shell from the side, naming the parts. 

From the "mouth" of the shell the soft parts of the 
snail may be protruded, the large foot being the last to 
disappear during contraction and the first to leave the shell 
as the animal again expands. To the upper side of the 
foot a horny lid, or operculum, is attached, which may effec- 
tually close the opening of the mouth. 

As the animal crawls about, the shell is carried upon its 



6o Invertebrate Zoology, 

back, the canal being directed forward, the spire backward. 
The opening of the shell is then on the right side. 

Examine an animal that has been removed from the shell, 
and compare the number of whorls made by the body with 
the same of the shell. 

The lower surface of the foot is somewhat wrinkled. It 
has, leading from its centre, an opening from the ''pedal 
gland.'' At the posterior and dorsal part of the foot, observe 
the attachment of the operculum. Extending anteriorly and 
dorsally, the substance of the foot merges into the head. 
The head is anteriorly provided with two laterally projecting 
and triangular flaps, the tentacles} Midway between the 
tentacles, but somewhat below them, is the opening of the 
mouth. Frequently the elongated proboscis projects from the 
mouth as a flexible tube, an inch or more in length. If the 
specimen being examined is a male, the large intromittent 
organ, or penis^ will be observed. It is situated a little to 
the right of and above the right tentacle. 

The collar is a circular fold of the mantle that entirely 
surrounds the body just posterior to the head. In life, it 
was applied to the lips of the shell, and by its activity the 
body of the shell (middle layer as well as the epidermis) 
was elaborated. At a point corresponding to the canal the 
inner part of the collar is produced into a groove-like siphon. 

If the collar is elevated along its antero-dorsal portion, a 
large chamber, the inantle cavity, will be exposed. 

The soft parts of the animal, extending into the spire, are 
collectively spoken of as the ''visceral mass,'' It should be 
borne in mind that the outer surface of each whorl corre- 
sponds to the left side of the animal, while the inner surface, 
next the cohimella, is the right side. 

1 On the lateral edge of each tentacle is the small deeply-pigmented eye. 



A CepJialopJioroics Mollnsk, 6i 

The outlines of the following organs may be distinguished 
through the somewhat transparent walls. 

The liver or digestive gland extends as a dark green mass, 
from the apex of the spire, of which it forms the larger 
part, to a point two revolutions lower down. It bears on 
its dorsal surface the lighter sexual gland, testis or ovary, 
the sexes in this univalve being separate. 

On the external surface of the liver the stomach is often 
to be seen as a curved body somewhat less than the sexual 
gland in size. Extending anteriorly from the liver, and con- 
fined more to the outer portion of the whorl, is the dark- 
colored 7'enal oigan or kidney. The outline of this organ, 
when viewed from above, is triangular, the apex being di- 
rected towards the columella, while the base extends laterally. 
Viewed from the side, the base of the triangle is seen to rest 
upon the liver, posteriorly ; upon the pericardial cha?nl?er, 
ventrally ; and upon the roof of the mantle chamber, ante- 
riorly. The renal organ is divided into a smaller tubuliferous 
portion, which lies against the pericardium, and a larger acin- 
ous portion, \n\\\c\\ hes above and around the first. ^ The line 
separating the two runs parallel with the upper edge of the 
pericardium. The pericardial chamber is somewhat cres- 
centic in outline, and is about the size of one of the tentacles. 

If the specimen being examined is a female, the roof of 
the mantle chamber presents on its dorsal surface a long, 
large elevation of light cream-color, extending from the 
liver, and internal to the kidney, nearly to the free edge of 
the collar. This elevation is the nidamcntal gland. Through 
its activity the long egg- strings are manufactured. Lying 
parallel to, but outside of and below the nidamcntal gland 
(nearer to the siphon tube), the location of the gill is clearly 

1 The function of the tubuliferous portion is uncertain. It is prob- 
ably not excretory. 



62 Invertebrate Zoology, 

seen. It is a large crescentic area, often slightly depressed. 
On the inside of the visceral mass, and extending somewhat 
parallel to the nidamental gland, is the large columellar mus- 
cle, by means of which the animal retains its hold upon the 
columella of the shell. 

Make drawings of the animal as seen from in front and 
as seen from the outer and inner sides. 

The Anatomy of the Mantle Cavity. — With a pair of 
scissors slit open the roof of the mantle chamber along a 
median line extending parallel to the upper edge of the 
gill. Reflect the flaps and observe, on the inner side of 
the left, the extent of the single large lamellate gill What 
is the arrangement of the branchial lamellce ? Immediately 
below the gill is a smaller organ, somewhat similar in out- 
line and structure. It is the osphradijim or olfactory organ. 
On the inner surface of the right flap the external opening 
of the rectum will be noted. It is at the apex of a short 
anteriorly directed tube. 

If the specimen is a female, the external opening of the 
oviduct will be found at the apex of an elevation near, though 
a little lower than, the anal papilla. Pass a flexible probe 
(a guarded bristle) into the opening. 

Males are somewhat smaller than the females, and may 
be readily distinguished by the intromittent organ. Lead- 
ing out from the base of the penis, and inclining towards 
the right, until it finally reaches the groove made by the 
union of the roof of the mantle chamber to the body, is a 
clearly defined ridge which marks the course taken by the 
vas deferens. Trace the vas deferens to the upper portion 
of the mantle chamber. 

In both sexes a large gland, the hypobranchial or adrectal 



A CephalopJwroiLS Molhcsk, 63 

gland, occurs as a series of tranverse folds along the roof 
of the mantle chamber. In the female the gland extends 
between the gill and the nidamental gland. 

At the very apex of the mantle chamber a slit-like open- 
ing will be found. This opening leads from the cavity of 
the renal organ. 

Make a drawing that will illustrate the anatomy of the 
mantle chamber. 

Internal Anatomy. — The systems of organs may be 
dissected in the following order : — 

{a) The Circulatory System. — Though it is well to 
use a hypodermic syringe with some colored liquid for trac- 
ing out the arteries and veins, the larger blood-vessels may 
be located in the uninjected specimen. — The branchial 
vein, seen from without, is a transparent line running 
along the lower side of the area which we know to be that 
of the gill. It may be followed nearly to the pericardium, 
where it unites with a renal vein that returns the blood 
from the lower, tubuliferous portion of the renal organ. 
The common vein empties into the atcricle of the heart. 

With a pair of scissors carefully open the pericardial 
chamber, and gently hft the heart from the cavity. The 
auricle will appear as an anterior division, thin- walled and 
collapsed. The ventricle, lying posteriorly, is much larger, 
and is provided with strong muscular walls. From the ven- 
tricle arise two arteries. These pass from its posterior 
end and convey blood to all parts of the animal. The vis- 
ceral arfery passes upwards, through the substance of the 
liver, giving off branches to the stomach and reproductive 
gland. By the careful use of probes the visceral artery 
is not difficult to trace. The aorta, the second artery, 



64 Invertebrate Zoology. 

makes an abrupt turn downwards and forwards, and passes 
towards the head. It soon enlarges and forms a secondary 
heart which hes, as dissection will show, to the left of, upon 
and to the right of, the oesophagus. Large branches are 
given off to the muscles of the foot, siphon, and to the head. 

Make a drawing of the heart and principal blood-vessels. 

Cut the heart in two and reflect, exposing the pericardial 
chamber. Note the serous hning, and especially the open- 
ing which leads into the renal organ. This opening, which 
is of considerable morphological significance, will be found 
somewhat below and inside of the point of entrance of the 
branchial and the renal veins, and near the deepest point of 
the pericardial chamber. 

Make a drawing of the interior of the pericardium. 

(^) The Excretory System. — The location of the glan- 
dular and of the tubuliferous portions of the kidney have 
already been noted. With a small pair of scissors cut along 
their common line of union, opening the chamber of the 
kidney. Observe the numerous parallel lines of tubules 
which make up the substance of the lower, tubuliferous por- 
tion. The larger, acinous portion of the kidney is made up 
of large lobules over which blood-vessels ramify, on their 
course from the upper part of the body to the gill. Look 
for the large opening leading from the renal to the mantle 
chamber, and also for the smaller opening which leads from 
the pericardial chamber. 

Make a drawing of the glandular organs of the kidney. 

Carefully remove the acinous portion of the renal organ. 

{c) The Reproductive System. — If the specimen being 
examined is a female, the ovary will be found as already, 
noted. Trace the ovidtut as it leaves the lower inner side 



A CcphalopJioroiis Mo Husk. 65 

of the ovary and passes down to the nidamental gland. In 
the Hving animal it rests against the columella. Follow the 
course through the lumen of the nidamental gland to the 
exterior. Open the ovary and note the ultimate branches of 
the oviduct and the numerous eggs. 

Make drawings that will illustrate the anatomy of the 
ovary and the course of the oviduct. 

The testis of the male lies in the same place as does the 
ovary of the female, and its duct, the ras deferens, pursues a 
similar course along the inner surface of the liver to that 
taken by the oviduct. The course along the floor of the 
mantle chamber has already been noted. 

Draw. 

{d) The Digestive System. — Select a specimen that has 
been killed while the proboscis remained protruded and 
note the terminal inoicth-opening, and the lingual ribbon or 
odontophore, projecting slightly from its lower side. With a 
pair of scissors slit open the proboscis along its mid-dorsal 
line, taking care to cut only through the skin. Immediately 
below the incision, the light-colored cesophagus will be seen 
as a straight tube. It extends from its opening into the 
pharyngeal cavity, immediately over the end of the odonto- 
phore, to the upper end of the proboscis, where it abruptly 
dips into the substance of the body. Note the small fibres 
that attach it to the integument, and which, at its outer end, 
are deeply colored, and may, by their contractility, give the 
organ a pumping function. Extending from the base of the 
proboscis into the substance of the body are a pair of white 
muscle bundles, the rigJit and left retractors of tJie proboscis. 

Below the cesophagus lies the dee})-colore(l jnuscular mass 
that brings about the movement of the lingual ribbon. 



66 Invertebrate Zoology, 

Draw. 

The odontophoral or radular protractors are muscle 
fibres which extend from the lower side of the muscular 
mass to the inner surface of the integument, near the free end 
of the proboscis. The radular retractors are a series of 
fibres extending dorsally from the proximal end of the 
cylinder to the inner surface of the integument, near the 
base of the proboscis. 

Having opened the oesophagus, free it from the underlying 
muscular mass, and note the transverse fibres of a thin 
muscle sheet that rested below the middle third of the 
oesophagus and gives attachment to the radular protractors 
along its lateral edge. Observe that the radula extends 
under the muscle from near the base of the proboscis to its 
free end, and that the obHquely disposed radular retractors 
also extend under the muscle sheet. 

Carefully slit open the muscle sheet and note the place of 
insertion of the radular retractors along the sides of the 
radula. 

The lower surface of the radula rests upon a pair of 
elongated odontophoral cartilages^ the retractor muscles 
of which extend proximally and below the radular retractors 
to a tendinous ring, which also gives attachment to the white 
fibres of the retractors of the proboscis. On the ventral 
side of the muscular mass the ve?it?^al retractor of the radula 
will be noted. It is a small muscle, lying between the 
odontophoral cartilages, and by its contraction the dorsal 
surface of the radula is brought down over the pulley-like 
ends of the odontophoral cartilages. 

Make a drawing that will illustrate the structure of the 
radular apparatus. 

The oesophagus passes between the mass of white re- 



A Cephalophoroiis Mollitsk, 6j 

tractors of the proboscis and midway between the large yel- 
low salivary glands. The ducts from the salivary glands 
appear as two delicate tubes extending one on either side of 
the oesophagus as it passes down the proboscis. 

Draw. 

At a short distance beyond the salivary glands the oesoph- 
agus is surrounded by the ora?ige-colored ganglia of the ner- 
vous system. A little posterior to the oesophageal nerve- 
ring, the alimentary tube receives the duct from a dehcate, 
elongated gland, the ''pancreas,'" which lies to the right side 
of and upon an enlarged section of the alimentary tract, the 
c?'op. The crop becomes smaller in diameter as it ap- 
proaches the liver, into the lower portion of which it courses, 
and becoming again enlarged, forms the '' stomachy The 
walls of the stomach may be seen without dissection as a 
whitish tract on the outer surface of the Hver. 

If the stomach is opened and the contents washed away, 
the large hepatic ducts will be found. How many ducts are 
there ? After passing along the lower side of the liver, the 
stomach bends abruptly upward and forward, and thence, as 
the intestine and rectum, runs to its external opening parallel 
to the crop and oesophagus. Is the epithehal lining of the 
rectum in any way specialized ? 

Make drawings that will illustrate the course of the ali- 
mentary tract. 

{e) The Nervous System. — The nervous system of the 
Cephalophorous or Gasteropod mollusks consists of a series 
q{ gariglia, chiefly arranged around the oesophagus, and of a 
number of radiating no've-cords. — The circle of ganglia sur- 
round the oesophagus somewhat in front of the duct of the 
'' pancreatic gland," and when viewed from above present 



68 Invertebrate Zoology. 

considerable bilateral asymmetry. If the anterior part of 
the oesophagus is turned back, however, the lower side of 
the ganglionic mass will be found to be made up of two 
nearly equal halves. 

Lying ventrally are the small buccal ganglia, a pair of 
spherical bodies somewhat in front of the remaining ganglia 
and giving origin to a number of nerve-strands that pass to 
the pharyngeal apparatus. A buccal commissure runs beneath 
the oesophagus and connects the right with the left ganglion. 

Also, on the ventral side of the oesophagus are the much 
\2iXgQX pedal ganglia. These lie, fused together, a little pos- 
terior to the buccal ganglia, and from them large strands of 
nerves pass to the right and left halves of the foot. 

Cerebro-pedal connectives pass from the pedal ganglia 
dorsally, partially encircling the oesophagus, and uniting with 
the cei^ebral ganglia. The cerebral ganglia rest dorso-later- 
ally upon the oesophagus, and are united dorsally by the 
cerebral coinmissure. Nerves pass from the cerebral ganglia 
to the region of the head. Cerebro-buccal connectives unite 
the buccal and cerebral ganglia. 

The left cerebral ganglion is in union ventrally and pos- 
teriorly with the left pleural ganglion, which rests anteriorly 
upon the posterior part of the left pedal ganglion. 

The right cerebral ganglion at first appears to be some- 
what larger than its fellow. Examination will show that this 
is because of its partial fusion with the right plural ganglion, 
which lies immediately ventral and posterior to it. 

At the posterior edge of the right pleural ganglion, the 
pear-shaped right visceral or supra-intestinal ganglion is 
seen to be attached. It lies almost directly upon the dorsal 
surface of the oesophagus, and gives off several branches, of 
which two go to the osphradium, and a third passes pos- 



A CeplialopJioroiis Mollask. 69 

teriorly in a line nearly parallel to the course taken by the 
digestive tract. This posterior band forms one half of the 
so-called visce?'al loop and leads to the abdominal gan- 
glion, located far up in the substance of the body near the 
nephridial opening. 

The left visceral or sub-intestinal ganglion lies on the right 
side of the oesophagus, below the right pleural ganglion, and 
posterior to the right pedal ganglion. A broad band, the 
left visceropleural commissure, will be observed to lead from 
the left visceral ganglion to the left pleural ganglion, passing 
below the oesophagus just back of the pedal ganglia. The 
left visceral ganglion gives rise to the left half of the visceral 
loop, which passes posteriorly to join the abdominal ganglion 
already noted. On its course it gives off a branch to the 
columellar muscle. 

The pleural ganglia give off nerves which pass to the 
lateral walls of the body and to siphon and collar. 

Make a series of drawings of the nervous systems. 



70 Invertebrate Zoology, 



A CEPHALOPODOUS MOLLUSK 

(JLoligo pealit). 

External Anatomy. — Note the elongated body, sepa- 
rated from the movable head by a constricted neck. The 
integument is abundantly supplied with chro7natophores. 
Though not of the usual morphological significance, observe 
that there is an anterior and a posterior end, and a dorsal 
and a ventral surface. What is the shape and attachment 
of the terminal y^;zj- ? Demonstrate that there is an opening 
between the neck and the " collar " into a central chamber, 
the mantle cavity. What is the position of the eyes ? Are 
they provided with lids ? How many arms are there ? Are 
all of the arms of the same structure? How many rows of 
suckers are there on the shorter arms? On the longer? 
Do you find the mouth ? The opening of the siphon-tube ? 
Just back of each eye, note the fold of the olfactory oi^gan. 
What is its extent? Note the median, dorsal projection of 
the collar. Turn it back, and note that it is stiffened by the 
presence of a horny structure. 

Open the animal along the mid-dorsal line. The horny 
structure, pen^ will be found to extend the entire length. 
Remove the pen. 

Make a drawing of the animal as seen from the left side, 
putting in as much detail as possible and naming the parts. 
Also make a drawing of the pen. 



A Cephalopodoiis Mo litis k. 71 

Examine one of the larger suckers. Is it sessile or 
mounted on a peduncle ? Note the horny ring. Is the 
margin of the ring entire or serrate ? Make a longitudinal 
section through the sucker and its fleshy //j"/^//. 

Draw the side view of the section. 

Internal Anatomy. — Carefully open a male specimen, 

a little to one side of the mid-ventral hne, exposing the 
mantle cavity. Pass a large probe through the opening of 
the siphon. Do you find the large retractor muscles of the 
siphon? Trace them to their posterior points of attach- 
ment. On each side of the siphon note the lateral sipJional 
blind-sacs. What is their function ? Immediately posterior 
to the siphon note the tube-like rectum. 

The anus, at the most anterior point of the rectum, will 
be found guarded by two lateral, leaf-like valves. Carefully 
inject water into the rectum, and note the outline of the 
organ. 

Immediately dorsal to the rectum is a dark-colored sac, 
the ink-sac. Slit open the anterior end of the rectum, 
along its mid- ventral line, and note the point of entrance of 
the tube from the ink-sac. 

Lying along each side of the mantle cavity, and parallel 
to the retractors of the siphon, are the gills. How is each 
gill attached? Do you find, at the base of each, a disc- 
shaped branchial heart ? The inedian mantle a?'tery will be 
noted, as a cord-like tube, extending from a point midway 
between the branchial hearts, across the mantle cavity to the 
inner side of the mantle. It marks the anterior limit of a 
fnedian mesenteric fold that extends from it posteriorly. 

Looking through the transparent tissue that covers the 
viscera, a pair of underlying urinary organs, or nephridia, 



72 Invertebrate Zoology, 

will be seen. Anteriorly, each organ opens through a small 
pore that thus leads from the nephridium to the mantle 
cavity. Each pore Hes near the median line, some little 
distance in front of the branchial heart, and marks the 
anterior end of the nephridial chamber. The posterior and 
broader end of the chamber lies just medially of the branchial 
heart, the right and left nearly meeting in the median line. 

Two arteries, lateral mantle arteries, will be noticed (one 
on each side), extending laterally and posteriorly, from near 
the point where the median mantle artery leaves the visceral 
mass, to the internal surface of the mantle. Lying laterally 
to each lateral mantle artery is a much larger thin-walled 
posterior vena cava. This organ is often filled with blood 
that has been received from the posterior mantle veins which 
lie parallel to the mantle artery. The cone-shaped posterior 
portion of the mantle cavity is filled up with the voluminous 
visceral sac and the sexual organs. 

Make an outhne drawing of the organs as they naturally 
lie in the mantle cavity. 

The Circulatory System. — By the use of a hypodermic 
syringe the circulatory system may be injected and the fol- 
lowing points determined. 

Each post-cava empties its blood into the branchial heart of 
the same side, which also receives the blood that has been re- 
turned from the anterior portion of the animal through the/;r- 
cavce. The latter traverse the glandular walls of the nephridial 
chambers. Each branchial heart also receives an anterior 
mantle vein, returning blood from the anterior portion of the 
mantle. Impure blood is forced from the branchial heart 
to the gills along the afferent bra7ichial vessel which traverses 
the edge of the gill that is directed towards the mantle. 



A CepJialopodoiis Mollusk. 



/J 



The pre-cavae unite just in front of the nephridial organs 
and form the common vena cava. This vessel Hes an- 
teriorly in the median line, just dorsal to the ink-sac and 
midway between the siphonal retractors. It returns the 
blood from the ink-sac, liver, oesophagus, and head. 

The systemic heai't lies in the median line between the 
posterior ends of the nephridial organs and receives blood 
from the rigJit and left efferent branchial vessels, which 
course along the free edge of the gill. 

The systemic heart gives off an anterior and ?. posterior 
aorta. The former passes directly to the head, dividing at 
the neck into a 7'ight and a left branch. On its course it 
gives off certain branches to the digestive organs. The 
posterior aorta soon divides into the median and lateral 
mantle arteries already noted. 

The cavae rest dorsally on a delicate flask-shaped bilateral 
organ of considerable size, the ''spleen'' 

Make drawings illustrating the course of the blood-vessels. 

The Digestive System. — Note the large chitinousy'^rzc'^-, 
situated at the base of the circle of arms. Which jaw is 
larger? Open the mouth and note the lingual ribbon or 
odontophore. What is its position? Pass a probe down the 
narrow (esophagus, and cutting along the mid-ventral line of 
the head and neck, follow the oesophagus to its entrance into 
the stomach. On its way it is accompanied for a short dis- 
tance, along its ventral side, by the duct from the median 
salivary gland, diSmdiW body which may be found enfolded 
in the anterior end of the liver. The lateral salivary 
glands lie on the posterior surface of the buccal-mass. The 
li7'er is a large gland that extends posteriorly from near the 
spherical buccal-mass to a point dorsal to the nephridial 



74 Invertebrate Zoology. 

openings. It lies between and dorsal to the siphonal re- 
tractors, and is pierced at its anterior end by the oesophagus, 
which courses along its dorsal surface. 

The oesophagus finally enters the smaller, more muscular, 
cardiac portion of the stomach. By blowing with a blow- 
pipe into the cardiac portion, the much larger and thin- 
walled gast7ic sac will become inflated. This organ is a 
^* blind-sac " and extends to the posterior end of the mantle 
cavity. It often contains partially digested food — bits of 
fish, etc. 

Trace the intestine from its origin, near where the oesopha- 
gus enters the stomach, to the rectum. If the gastric sac is 
already filled with water, it may be rolled from its original 
position, clearly showing its relations to the other neighbor- 
ing organs. 

Make a drawing of the entire digestive system as seen from 
below, and also as seen from the side, naming all the parts. 

The Muscular System. — The Cephalopods are most 
active Invertebrates and the muscular system is correlatively 
developed. Muscle tissue largely makes up the outer sub- 
stance of the animal, though there is a remarkable lack of 
clearly defined muscle bundles. The retractors of the head 
and siphon are, however, more definitely isolated. 

Reproductive System of the Male. — As the gastric 
sac is partly removed, note on the posterior dorsal wall of 
the mantle cavity the large testis. It is firm in texture and 
somewhat elongate-oval in outline. Leading to the testis 
from the region of the cardiac stomach is an artery which 
pierces the delicate capsule in which the organ lies. At 
the left of the testis, the accessojy reproductive organs of the 
male are to be observed. They form an irregular mass 



A CepJialopodoiis Mollusk. 75 

from which a tube, the spermatophoric sac^ passes anteriorly 
to open through the penis. The latter is a tube of consider- 
able size, lying parallel to, and along the left side of, the 
rectum. The penis finally opens at a point about even with 
the anus. 

There extends from the spermatophoric sac, which is 
often filled with numerous small worm-like spermatophores, 
to the capsule of the testis, an elongated and much convo- 
luted tube, the vas deferens. It is, in places, considerably 
swollen and highly glandular. 

Make a drawing of the male sexual organs, naming the 
parts. 

The Reproductive System of the Female. — If the 

mantle cavity of a female specimen is opened in the mid- 
ventral line, the sex may be at once determined by the 
presence of two large nidamental glafids, each about the 
size of one's Httle finger and lying side by side along 
the median line, well towards the anterior of the mande 
cavity. Each gland has an anterior opening through which 
the gelatinous substance of the egg-capsuk is extruded. 
Lying in front of the nidamental glands are the smaller, 
reniform accessory glands, which rest laterally upon the sides 
of the rectum and ink-bag. 

The large funnel-shaped opening of the oviduct will be 
seen at the left, on a line with the openings from the nida- 
mental and accessory glands. Pass a probe into the ovidu- 
cal opening, and trace the duct below the left gill into the 
large ovidiical gland. It is situated on the left of the pos- 
terior end of the nidamental gland. From the central point 
of the oviducal gland the more constricted oviduct will ])e 
seen. It passes posteriorly towards the mid-ventral line. 



"jS Invertebrate Zoology. 

Follow the oviduct far back and note the abrupt turn in 
its course as it bends anteriorly. Trace it to its opening 
into the capsule of the ovary. The ovary lies along the 
dorsum and extends anteriorly from near the posterior end 
of the animal to a point dorsal to the external opening of 
the oviduct. In its substance are to be seen the eggs or ova^ 
in varying stages of maturation. 

The Excretory System. — The cavities and the external 
openings of the nephridia have already been noted. Such 
glandular tissue as i*s present is concentrated along the sides 
of the venae cavae. 

The Nervous System. — Observe on each side of the 
animal, at a point on the inner surface of the mantle just 
anterior to the attachment of the retractors of the head, the 
large stellate ganglia. From these ganglia radiating nerves 
may be traced to different portions of the mantle and, run- 
ning anteriorly from each, through the retractor of the same 
side, and thence to the infra- oesophageal ganglion, are the 
right and the left pleiwal nerves. Carefully trace these 
nerves to the cartilaginous support of the head, and then 
remove the tissue from the ventral side of the eyes until the 
enormous optie ganglia are exposed. 

Lying ventrally, between the optic ganglia, and protected 
by cartilage, are the fused /(?^rt;/, pleicral, and visceral ganglia. 
They form the ijif -a- oesophageal mass. 

With a sharp scalpel carefully slice away the ventral carti- 
lage, exposing the deep-lying nervous mass. Note, as the 
cartilage is being removed, the central cavities or auditory 
chambers. 

The infra-oesophageal mass is prolonged anteriorly into 
the pro-pedal ganglia, which give rise to ten radiating 



A Ceplialopodoiis JMollitsk. yy 

nerves which pass to the arms. The sipho7ial nerves are 
given off from the lower portion of the infra-oesophageal 
mass, while the pleural and visceral nerves arise more 
posteriorly. 

From the smaller supra-o^sophageal ganglion a pair of 
very minute connectives extend to the posterior surface 
of the buccal-mass, where they end, immediately over the 
oesophagus, in a pair of small supra-biiccal ganglia. From 
the supra-buccal ganglia fibres extend around the oesophagus 
to the infra-buccal ganglia. The latter are of about the 
same size as the supra-buccal pair, and are united below the 
oesophagus by a commissure. 

Make drawings of the ventral, lateral, and dorsal view^s of 
the brain. 



y8 Invertebrate Zoology. 



THE LOBSTER 1 

{Homarus americanus). 

External Anatomy. — Is the animal perfectly '^ bilater- 
ally symmetrical " ? What characters distinguish the anterior 
portion of the animal from the posterior? It will be ob- 
served that the latter, the abdomen, is segmented. Look 
carefully and see if there are traces of segmentation in the 
anterior portion, the cephalothorax. Is the number of ab- 
dominal segments constant? 

Has each abdominal segment a pair of appendages? Do 
they all take their origin from similar points of the several 
segments? The ventral piece lying between each pair of 
appendages is called the steinium. The dorsal portion is 
the tergum. The ventrally projecting lateral lobes are the 
pleui'ons. The epi7ne7'on is a piece, more clearly seen on the 
first abdominal segment, that lies ventrally between the ap- 
pendage and the pleuron. Note any specialization of any 

1 The lobster has been here introduced for several reasons. — Its gen- 
eralized structure, large size, and the easiness with which its organs may 
be dissected make it a most convenient animal for the demonstration 
of not only arthropod morphology, but of general Invertebrate anatomy. 
It is, moreover, a typical crustacean, and in a shorter course might be 
studied as a representative of the entire Class. The Crustacea considered 
farther on are especially valuable for comparative study. 



TJie Lobster, 79 

abdominal segment and, if possible, give a reason for the 
same. 

Is there anything to show that the last cephalothoracic 
appendage is homologous with the abdominal appendages ? 
The latter have been called pleopoda. If the homology 
can be shown for the last, it must also be claimed for the 
remaining cephalothoracic appendages of equivalent origin 
and structure. How many such appendages are there? 
(Answer the question by comparing points of origin, num- 
ber of joints, position of sensitive hairs, and number and 
position of protective spines. It will probably be concluded 
that there are five pairs closely resembling each other.) Why 
the remarkable enlargement of the anterior pair, \\\tfo?reps? 
Do the five pairs of appendages arise from five segments? 
Will you admit of the '^ Rule of Savigny " : '^ A pair of ap- 
pendages represents a segment, though segments may occur 
without appendages"? How many segments, then, are there 
from the posterior end of the body to the forceps ? 

The appendages lying immediately anterior to the forceps 
are more or less specialized. They may be pressed down 
one after the other, like leaves of a book, and if found 
homologous with the appendages already examined, their 
number will indicate the number of supporting segments. 

The most posterior, the third maxilliped, is in part like one 
of the ambulatory appendages already studied. Examine 
its point of origin, count its joints, etc. The immediately 
anterior, second maxilliped, is not remarkably different from 
the third, though they^r.^V maxilliped is considerably altered. 

The line separating the maxillipeds from the anteriorly 
lying second maxilhe divides the head from the thorax. 
There are two pairs of maxilKx, the second, broad and leaf- 
like ; they^/'j-/, smaller and tricleft. 



. 8o Invertebrate Zoology. 

In front of the first maxillae are the strong jaws or man- 
dibles, each provided with a jointed accessory portion, the 
palpus. 

Two pair of antennce lie somewhat in front of the jaws. 
The first antennce are shorter and biramous ; the second^ 
longer and with only a single filament. 

The compound eyes are borne on stalks which are, by 
some, considered to represent appendages. Beginning with 
the eye-stalks, enumerate the segments of the entire animal. 

Find the following openings : (d) The openings of the 
auditojy organ, each situated at the base of the first antennae 
and opening from the upper surface, {b) Of the excretory 
organs or green glands, on the lower side of the second an- 
tennae, {c) The mouth, between the mandibles, i^d) The 
oviducts, in females at the base of the third pair of ambula- 
tory appendages, {e) The openings into the receptive ap- 
paratus, if the specimen is a female, in the angles of the 
heart-shaped structure between the next succeeding pair of 
appendages. (/) The seminal openings of the male, at the 
bases of the last pair of thoracic appendages, {g^ The anal 
opening m the last segment {telso?t) of the abdomen. 

Is there anything to show that some of the paired open- 
ings may be homologous ? 

Comparative Study of the Appendages. — Examine 
one of the appendages of the fourth abdominal segment. It 
will be found to consist of an elongated basal portion, the 
p7^otopodite, bearing two blades, the endopodite within, and 
the exopodite without. Remove the left appendage where it 
joins the body and draw it as seen from in front, naming the 
parts. Compare with the appendages of the second, third, 
and fifth abdominal segments. Compare now with the first 



The Lobster, 8i 

and sixth. The appendages of the first abdominal segment 
are different in the two sexes. Do you find any trace of 
appendages on the terminal segment or telson? 

Examine one of the thoracic appendages and endeavor to 
homologize the parts with the parts of the pleopoda. Pass 
to the third maxilhped and see if it has a protopodite, an 
exopodite, and an endopodite. Return now to the ambula- 
tory appendage and see if you are better able to homologize 
its parts, so far as they are present, with parts of the abdomi- 
nal appendage. (The ambulatory appendage is really an 
endopodite supported on a strengthened protopodite.) 

Carefully remove the second ambulatory appendage of the 
left side and draw it as seen from the front, naming the 
parts. The proximal part of the protopodite bears a finely 
lamellate gill and a posteriorly directed membranous out- 
growth, \hQ flabellinn. 

Remove the remaining ambulatory appendages of the 
same side and see if all agree in structure. (Other gills sit- 
uated higher up, on the epimera, will be considered later.) 

Has the thi?'d maxilliped a gill ? A flabellum ? Remove, 
and draw as seen anteriorly, naming the parts. 

After carefully removing the second maxilliped and noting 
the rudimentary condition of the gill, the reduced flabellum, 
and the number of divisions of the entopodite, draw as 
above directed. 

The first maxilliped is without a gill, though its flabellum 
is remarkably developed. The flattened, elongated exopo- 
dite and endopodite extend anteriorly from the lateral 
angle, while the internal part of the protopodite is greatly 
enlarged and lobe-like. 

Draw. 

The second maxilla is even further altered : no gill is 



82 Invertebrate Zoology, 

present. The flabellum is indurated by a deposit of lime and 
stiffened by its fusion with the exopodite. What is the 
probable function of this the most anterior flabellum ? The 
endopodite resembles the same of the first maxilliped. The 
protopodite is divided into four long inwardly- projecting 
lobes. 

Draw. 

After identifying the parts of the first maxilla^ draw and 
name, taking care not to be confused by the fan-like out- 
growths of the lower lip. 

The body of each mandible represents the protopodite, 
while the palpus represents the endopodite. 

Draw as seen from in front, naming the parts. 

The second anten7ia presents a modification of the same 
double structure that has been noted in the other appen- 
dages. The protopodite bears an exopodite, a mere mov- 
able scale, and a much elongated endopodite, which func- 
tions as a tactile organ. 

Draw. 

The first antenna, the antenmile, is in the adult also bira- 
mous, though primitively it is uniramous. 

Draw. 

Morphology of the CarapacCo — It has probably been 
noted that a transverse groove divides the anterior portion 
of the cephalothorax from the posterior. The carapace, 
then, probably represents the fusion of terga, and our prob- 
lem is to find out which have become fused. 

If the groove be followed ventrally and anteriorly, it will 
lead to a septum between the second antennae and the man- 
dibles. It is probable, then, that the groove marks the 
dividing line between these two segments^ second antennal 



Tlie Lobster, 83 

and mandibular. We know that in front of the groove 
three segments are represented, because related Crusta- 
ceans {^Squilla, Eupagii7^us, Gebia^ Callianassa) show these 
three segments more or less free, and in the lobster there 
are three pairs of appendages. It is probable that in the 
lobster the terga were also once free though now consoHdated. 

Elevate the free edges of the carapace and give reasons, 
if you have any, for considering them homologous with the 
pleura. Note the marginal hairs. Where are they most 
abundant ? Their function ? With a strong knife cut away 
all the right side which lies posterior and ventral to the 
groove. Note that the inner layer is membranous. Is it 
continuous at the margin with the outer layer? How far 
dorsally does the membranous part extend? Follow the 
line of its union with the epimera. 

The space between the pleural piece and the epimera is 
the gill or branchial chamber. How many gills are there 
arising from the thoracic protopodites? Carefully remove 
these podobi^anchice with their associated flabella, keeping a 
record of their position. Above each exposed protopodite 
is a membranous interarticular viemb^'ane which bears the 
arthrobi^anchicE. Record the number and position of the 
arthrobranchise. Above, are the ioMX plcurobrancliicc. They 
belong to which segments ? 

Granting that the transverse groove marks the dividing line 
between two segments, it is reasonable to suppose that the 
part lying immediately behind it must represent a portion of 
the tergum and pleura of the mandibular segment. The 
fused thoracic epimera now being exposed, it is clear that 
the posterior portion of the cara]:)ace is certainly independent 
of the six posterior thoracic rings. To just which of the 
remaining segments, mandibular, maxillary or maxillipedal, 



84 Invertebrate Zoology. 

the posterior part of the carapace does belong is somewhat 
doubtful. 

Internal Anatomy. — With a strong pair of shears care- 
fully remove the calcareous shell from the dorsal half of the 
body, from the rostrum to the telson, noting the points 
where the muscles are attached. Have the attachments in 
any way affected the even contour of the exoskeleton? 
Examine still further the internal face of the removed por- 
tion of the carapace and see if there is anything to show that 
there are represented in it certain segments posterior to the 
groove. 

Remove the dorsally lying pigmented integU7nent, and 
also the superficial muscles, exposing the viscera. Note 
the large, anteriorly lying horny stomach. It is held in 
place by certain gastric muscles. Just back of the depres- 
sion in the carapace formed by the groove, the heart will be 
seen. In outline it is somewhat shield-shaped, three angles 
being directed anteriorly and a single rounded angle project- 
ing posteriorly. Two small, oblique openings will be noticed 
on its dorsal side, near the median line. 

Do you find the elongated sexual glands extending on 
either side from near the lateral angles of the stomach to 
about the middle of the abdomen? Is the right gland in 
communication with the left ? If the specimen is a female, 
the eggs may be seen through the transparent ovarian 
walls. Examine the outer border of the organ and find 
ducts leading ventrally. 

Can you follow a blood-vessel, the superior abdominal 
artery^ leading posteriorly from the heart and extending to 
the telson? Immediately below, and somewhat covered by 
the sexual organs, is the intestine. 



Tlie Lobster, 85 

The liver is the voluminous organ, of light green color, 
that fills up the greater part of the thorax. Note the seg- 
mental arrangement of the thoracic and abdominal muscles. 
Carefully remove the tissues at the base of the second 
antennae, exposing the g?'ee?i glands. 

Draw the animal as seen from above, usiii^ only the 
lightest outlines, as the details are to be put in after further 
study. 

Remove the muscular and skeletogenous tissue from the 
lateral third of the left side of the body, thus giving a new 
view of the viscera. Lay the animal in water and note the 
boundaries of the organs already studied. 

Probe through the mouth into the stomach. What direc- 
tion does the short oesophagus take ? The larger, more chiti- 
nous, anterior or cai'diac portion of the stomach is separated 
from the posterior or pyloric portion by a groove running 
diagonally from the dorsal to the ventral line. Do you find 
that the insertion of muscles is in any way related to the 
hardened areas of the stomachic walls? Are there any 
pouch-like out-pushings of the pyloric portion? Is the 
pyloric portion chitinous ? The whole organ resembles the 
exoskeleton and is, indeed, formed from an in-pushing of 
the outer covering of the body. 

Pass to the posterior end of the alimentary tract and note 
that the rectum, the section lying behind the middle of the 
penultimate segment, is somewhat different from the straight 
mesenteron or intestifie, which connects it with the pyloric 
portion of the stomach. Inject water through the anus and 
distend the intestine. Do you find a dorsally projecting 
sac, the ccecum, arising from the hinder end of the mesen- 
teron? 

Find the duct which leads horn the left lobe of the 



86 Invertebrate Zoology. 

liver, or mesenteric gland, into the intestine. What is its 
extent? Cut the gland open and see if it has a lumen. 
Does the lumen communicate with the intestine? What is 
the plan upon which the organ is built up. 

Carefully finish the drawing of the alimentary tract and 
its diverticula. 

Remove the entire alimentary tract and float it out in 
clean water. Dissect away the anterior wall of the stomach 
and wash out the contents. Artificially work the gastric 
teeth together, thus demonstrating their function. Do you 
notice any apparatus that prevents the larger fragments of 
food from entering the deHcate intestine ? Do you find any 
organs which might, in function, distinguish between the 
nutritious and non-nutritious contents of the stomach ? Are 
sensory hairs present in the oesophagus ? 

Slit open the intestine, caecum, and rectum. Do you find 
any local differences in the lining membrane of the three 
portions ? 

Make a drawing of the interior of the right half of the 
stomach. 

Excretory System. — With great care remove the left 
green-gland. Do you find the following parts : A smaller, 
ventral, glandular portion, of a deep green color in the 
living animal? A very large saccular portion, the deH- 
cate diverticula of which extend as lobes over the ante- 
rior and lateral walls of the stomach? The urinary 
duct, leading to the opening at the base of the second 
antennae ? 

Reproductive System. — This may be worked out on 
the side of the animal which has not yet been injured. If the 



The Lobster, 87 

specimen is a female the essential reproductive organs are 
the ovaries. Their position, color, and relation to the other 
viscera, should be clearly determined. How are they held 
in place? Can water be injected into them through the 
openings at the bases of the ambulatory appendages? 
Examine the oviduct and note its course. Are the eggs in 
different portions of the organ of about the same size ? 

Make a longitudinal incision through the ovarian wall 
and examine the interior. How are the eggs held in place ? 
Is the wall of the oviduct in any way different from the 
same of the ovary? It is probable that it secretes a cover- 
ing for the eggs, as they are being extruded, which attaches 
them to the hairs of the abdominal appendages. 

Open the receptive apparatus and place some of the con- 
tained fluid on a microscope slide. Do you find, on exam- 
ining the preparation with a high power, that sper?7iatozoa 
are present? If the specimen which is being dissected 
measures ten inches in length, it will in all probability con- 
tain many of these male-cells, the structure of which is given 
below. 

Draw the ovary. 

Examine a male specimen. Note the position, color, and 
extent of the testes, the essential reproductive organs of the 
male. In what respect do they differ from the correlative 
structures of the female? Endeavor to inject through the 
external openings. Is the course taken by the vasa defer- 
eiitia in any way different from that taken by the oviducts? 
Do you find the median portion of the vasa deferentia 
enlarged? Can you induce the extrusion of the contents 
{spcrmatophore^ of tin's cnlari:(C(l portion? Slit o]^en one of 
the testes and place some of the contained fluid on a slide. 
Cover, and examine as above directed. 



88 Invertebrate Zoology, 

Each of the spermatozoa, or male-cells, will be found to 
consist of a somewhat cylindrical body, which is terminated 
at one end by a series of long spines. 

Make a drawing of one of the testes as seen from the side, 
representing the vas deferens, and the external opening. 

The Circulatory System. — The position of the heart 
has been already noted. In a specimen having the circula- 
tory system artificially injected with a colored fluid, note the 
pericardial sac, a delicate tissue surrounding the heart. It 
receives the blood from the branchice^ which then enters 
the heart through six cardiac apei'tures. The dorsal^ lateral, 
and ve7itral apertu?rs occupy positions as suggested by their 
names. 

The origins of the arteries, as they leave the heart, are as 
follows : — 

The superior abdominal artery passes directly posteriorly 
from the heart, resting on the sexual organs, intestine, and 
deeper muscles. How many branches does it give off to 
each abdominal segment? Does it send branches to the 
sexual organs? Intestine? Caecum? Note any terminal 
bifurcation. 

The sternal artery has its origin from the most anterior 
point of the superior abdominal artery. It passes ventrally 
to supply the lower portions of the body. On which side 
of the intestine does it pass ? 

The ophthalmic artery runs from the heart anteriorly. 
Does it give off branches to the stomach? Can you deter- 
mine its distribution in the anterior part of the head? 

The anten7tary arteries arise from near the antero-lateral 

1 Later dissection will show that the blood is returned from the 
branchiae through six bra^ichio- cardiac canals. 



The Lobster. 89 

angle of the heart. Each, in its course to the region of the 
antenna, gives off, besides others, a branch to the lateral 
walls of the stomach. Do you find the renal branchy dis- 
tributed to the green-glands? 

Draw in the circulatory system on the dorsal view of the 
animal already made, using a brush with hght carmine paint. 

Press to one side the viscera, which hide the duct of the 
mesenteric gland. A large artery, the hepatic^ will be seen. 
From what part of the heart does it take its origin? .Does 
it give off branches to other organs ? 

By the use of dots, rather than lines, designate its position 
on the drawing. 

Turn the animal on its back, and through the transparent 
wall of the abdomen note the inferior abdominal artery. 
With a strong knife or with scissors, cut away the abdominal 
sterna, and see if the artery sends out metameric branches. 
Follow the artery anteriorly. It will be found to receive its 
blood from the sternal artery, which also gives rise to an 
anterior branch. 

The anti'ro-7'entral artery passes along the mid-ventral 
line of the thorax. Name in order the branches that it 
gives off to the thoracic appendages. What is its anterior 
termination? 

From the ultimate subdivisions of the main arteries, above 
noted, the blood passes into certain sinuses, and from these 
is sent to the subdivisions of the gills, through the afferent 
branehial vessels, and there purified. Does your specimen 
show the afferent vessels? After being purified, the 
blood from the minute gill-filaments empties into the 
efferent branehial 7'essels which unite to form the bianeJiio- 
eaniiae eanals. The latter lead from the region of the 
thoracic epimera to the pericardium, where they empty 



90 Invertebrate Zoology. 

their contents. Does your specimen show the efferent 
branchial vessels ? The branchio-cardiac canals ? 

In the injected gills note the course taken by the large 
afferent and efferent vessels. Is the flabellum also supplied 
with axial blood-vessels ? Examine the gill with a lens and 
note the slender filaments. 

Make a drawing that will show the structure of the gill. 

The Nervous System. — The specimens have had many 
of the internal organs removed, but as the greater portion 
of the nervous system lies ventrally, it has not been injured. 
The system consists of a series of nervous centres, ox ganglia, 
connected together by longitudinal and transverse commis- 
sures. Work out the following : — 

The supra-oesophageal ganglia will be found beneath the 
rostrum at the base of the antennae. The right is intimately 
connected with the left. Extending posteriorly and sur- 
rounding the oesophagus, are the cireiim-oesophageal commis- 
sures, which are soon united by 

The infra- oesophageal ganglion which lies immediately 
behind the oesophagus. 

From the infra-oesophageal ganglion the longitudinal com- 
missures or connectives may be followed to the region of the 
telson. 

How many thoracic ganglia are there? How many 
abdominal ganglia? Are the gangUa of one series more 
closely approximated than those of the other? Does the 
number of ganglia in anyway correspond with the number 
of associated body segments ? Do you find nerves running 
from the ganglia to the surrounding tissues ? 

Make two drawings of the nervous system, one as it is 
seen from above, the other as it is seen from the side. 



A Phyllopod Cncstacean, 91 



A PHYLLOPOD CRUSTACEAN 

( B7'a n ch ipus v emails ) . 

External Anatomy. — Observe the elongated body. Is 
it distinctly segmented? Is it separated into a head, a 
thorax, and an abdomen ? The appendages are leaf-like 
(Phyllopod). They occur on which main division of the 
body? Are they represented on the other regions ? Observe 
the pair of flexible anterior antenncB. In the males the 
seeond anten?icE are enormously developed and form *^ clasp- 
ing organs." Large at the base, each second antenna soon 
becomes constricted, and forms an elongated chitinous rod. 
Find the homologues of the second antennae in the female. 

The upper lip, labriim, will be found as a median fold 
extending posteriorly from between the bases of the second 
antennae. Elevate the labrum and note that it covers the 
jaws or mandibles. In what plane do the mandibles move? 
Are the cutting edges specially hardened? Note the open- 
ing of the mouth. The maxlllce, relatively poorly developed, 
lie immediately posterior to the mouth. 

How many pairs of thoraele appendages are there ? Care- 
fully remove one of the first pair, and note that there is a 
basal portion, protopodite, which is extended distally by cer- 
tain lobes. The internal lobe, endopodite, is the lari^est and 
bears numerous setce along its inner and distal edge. Of the 
same general structure is the outer lobe or exopodite, which 



92 Invertebrate Zoology, 

bears several longer setae. External to and above the exop- 
odite is a small sac, the gill-sac. Above the gill-sac is the 
broad, paddle-shaped gilL 

Examine the remaining thoracic appendages. Are they 
all built upon the same plan? What functions do they 
perform ? Recall the parapodia of Nereis. 

At the anterior end of the abdomen are the external 
sextcal 07gans. In the female they will be seen to enclose 
the eggs. In the male a tubular organ is formed. Are the 
terminal fin-like organs comparable with the thoracic ap- 
pendages ? 

Make drawings of the specimen as seen from the side, 
and of the more important and characteristic parts. 

Digestive System. — Open a specimen along the mid- 
ventral line, and observe the course of the alimentary tract. 
It extends as a tube from the mouth to the anus. Does 
the anus open dorsally or ventrally? Note any local en- 
largements of the alimentary tract. 

Make a drawing of the tract. 

The Circulatory System consists of an elongated dor- 
sally lying tube, the heart. It is provided with numerous 
lateral slits, a pair for each surrounding segment, and 
extends from near the anterior end of the thorax to the 
posterior part of the abdomen. The blood enters the heart 
through the lateral slits, and is forced out throagh the 
anterior aorta into the sinuses of the body, finally reaching 
the lamellated gills, where it is aerated. After being purified, 
a system of channels conveys the blood to a pericardial 
sinus, from which it passes through the slits or ostia into the 
heart. 



A Pliyllopod Cmstaccan, 93 

The Excretory System. — A pair of so-called '^ shell- 
glands''' may function as renal organs, and have been com- 
pared with nephridia. They open to the exterior through 
two papillae, near the bases of the second maxillae. 

The Muscular System is well developed. Observe the 
extensor and retractor muscles of the abdomen. /\lso note, 
in the thorax, the presence of regularly arranged muscle 
bundles. Recall the arrangement in Nereis, 

The Nervous System. — Observe the minute, median 
ocellus. Below and on each side of it are the first antennae, 
the tactile organs. The compound eyes 2,xt large and promi- 
nent. Are they stalked? Examine carefully and note the 
facets. 

Make a drawing of the head, paying particular attention 
to the organs of special sense. 

Carefully remove the appendages from another specimen, 
using a pair of fine scissors. Cut the animal open along the 
mid-dorsal line, and remove the lateral walls of the thorax 
and abdomen, together with all. but the most anterior portion 
of the alimentary tract. Wash out the cavity with ninety- 
five per cent alcohol, and then place in absolute alcohol for 
one quarter of an hour. Remove from absolute alcohol and 
place in xylol. The delicate ventral chain of ganglia will 
soon take on a different appearance from the rest of the 
specimen. Note that there are two ganglia in each thoracic 
segment, each connected with its fellow by a cross conimis- 
su7r. The ganglia lying anterior and posterior to each other 
are united by lojigitiidiiial connectives. I^'ollow the chain 
into the abdomen and also anteriorly into the head. As 
in Nereis, it will be found to surround the oesophagus and 



94 Invertebrate Zoology, 

to pass above into the supra- oesophageal ganglion or brain. 
Trace the nerves from the brain to the ocellus and to the 
compound eyes. 

Make a drawing of the nervous system. 

The Reproductive System. — The '^brood-pouch" of 
the female has already been noted. The ovaries are paired 
organs, each lying parallel to the aHmentary tract, and extend- 
ing through a considerable portion of the thorax and abdomen. 
They are beautifully brought out by the adoption of the xylol 
method above described. Note, in the brood-sac, the large 
eggs. Do you find any pore through which the eggs may 
pass from the sac to the exterior? 

Make drawings of the female reproductive system. 

The extef^nal reproductive organs of the male are situated on 
the anterior portion of the abdomen. Each consists of a 
somewhat complicated apparatus, which is used in placing 
the spermatophores in the sacs of the female. The testes 
will be easily found as paired organs, of the same general 
structure as the ovaries, though of not equal extent. 

Draw the reproductive system of the male. 



A Free-Living Copcpod. 95 



A FREE-LIVING COPEPOD 

(^Cyclops sp.). 

Select a large female specimen (the females generally 
have a pair of ovisacs suspended from the body) , and exam- 
ine under a compound microscope. The body will be found 
to be well rounded, neither depressed nor compressed, con- 
siderably elongated, and clearly segmented. The divisions 
into cephalothorax and abdomen are at once apparent. The 
former consists of an anterior, unsegmented ca^^apace, behind 
which are four movable thoracic segments. Has the cara- 
pace a rostru?n ? Are the edges of the carapace free ? 
Are the several thoracic rings all of about the same size ? 

In the present sex the abdomen has four segments, though 
the first is in reaUty formed from two. Do you find any- 
thing to suggest that fusion has actually occurred ? In the 
smaller male there are five abdominal rings, the original 
structure being retained. 

How many filaments are there arising from the terminal 
abdominal styles ? Are there thoracic appendages ? Abdojn- 
inal appendages ? Note the position of the enlarged first 
antoinoi. Are they provided with hair-like setcc (olfactory 
hairs) ? Compare them with the smaller second antenna'. 
In the males the antenncc are reduced in size and function ize 
as clasping organs. 

Examine the swimming appendages of the posterior por- 



96 Invertebrate Zoology, 

tion of the cephalothorax. Four well-developed pairs will 
be found, each consisting of a basal portion and two free 
terminal blades. The fifth pair are reduced. The mouth 
partSf consisting of a pair of inandibles and two pairs of 
maxillcE^ are too small to be profitably studied at this time. 

Digestive System. — Specimens that have been feeding 
upon some colored substance (carmine) should be selected. 
They may be rendered inactive by placing a drop of ether 
in the watch-glass that contains them. The moitth, situate 
on the lower surface, just behind the origin of the antennae, 
will be found to lead into a large, somewhat thick-walled 
crop. From the crop the intestine extends in a direct 
course to the anus. Does the anus occupy a dorsal or a 
ventral position? Through which abdominal segment does 
it open ? 

Circulatory System. — Though in certain related forms 
there is a dorsally situated contractile heart, in the present 
form, and, indeed, in the greater number of Copepods, 
rhythmic contractions of the entire alimentary tract produce 
the circulation of the surrounding co^lomic fluid. 

Excretory System. — A pair of coiled tubes, the shell- 
glands, occupy lateral positions in the thorax and open to 
the exterior through pores at the bases of the maxillipeds. 
They are only to be seen in specially favorable specimens. 
The intestine probably has some excretory power, while the 
entire surface of the body may permit the escape of injurious 
gases, combining excretory and respiratory functions. 

The Muscular System is somewhat difficult to demon- 
strate. It consists of a series of regularly arranged fibres, 



A Free-Living Copepod, 97 

which bring about the movement of the second antennae, 
and other less important locomotor appendages. There 
are also two large muscular bands that forcibly flex the 
body. 

The Nervous System is too difficult of demonstration 
to be here considered. The olfactory hairs of the first 
antennae have been noted. The ocellus is the visual organ. 

The Reproductive System. — In the female the ovary 
is found to occupy a median dorsal position, extending as a 
somewhat elongated organ about two-thirds the length of 
the cephalothorax. Leading from the ovary to the external 
ovisacs are the oviducts. Each oviduct is a coiled structure, 
lying laterally to the ovary and often containing ova. Its 
external opening is through the first abdominal segment. 
The ova are fertilized from a rcccptaculum se??iinis, as they 
pass into the large ovisacs. How many eggs does each 
ovisac contain ? The young hatch in the interesting " Nau- 
plius stage." 

The sexual organs of the male consist of a median testis 
and two coiled, laterally extending vasa deferentia. Each 
vas deferens finally opens into a terminal receptacle, where 
the spermatozoa are collected, and form a sper)natophore. 
At time of coitus the spermatophore leaves the body of the 
male, through an opening in the first abdominal segment, 
and passes into the receptaeulum seminis. 

Make drawings of the dorsal and lateral views of the male 
and female. 



qS Inverteh'ate Zoology. 



A PARASITIC COPEPOD 

{Pandarus sinuatus). 

The species under consideration leads a parasitic life upon 
the external surface of the shark. Only females have been 
collected. Parasitism has wrought many interesting changes. 

External Anatomy. — When compared with the free- 
living Copepod, Cyclops, the present form will be found to 
have the body depressed, the cep halo thorax enlarged, and 
the posterior portion of the abdomen somewhat reduced. 
Compare the general outline with that of Cyclops. Is a 
rostrum present? Observe the location of the visual organ, 
and compare with Cyclops. Note the outline of the poste- 
rior three thoracic segments. The first abdominal segment 
is greatly enlarged, and within its transparent walls the coiled 
ovary and oviducts are to be seen. A rounded, flap-shaped 
piece terminates the body posteriorly. 

Make an enlarged drawing of the dorsal view. 

Examine the ventral surface and note its concavity. The 
first antennce appear as free, blade-like organs along the most 
anterior edge of the cephalothorax. Do they have flexible 
tips ? Are they provfded with sensory hairs ? At the base 
of each is a sucking disc. 

Having their origin nearer the median line, and bearing, 
laterally and posteriorly, a pair of suckers, are the small, 
hook-shaped second antennce. What is their function? 



A Parasitic Copcpod, 99 

The sticking p7'oboscis^ which is in part made up of the 
greatly modified mandidks, arises as a styhform organ, mid- 
way between the second antennae. It surrounds the oral 
opening. 

The fii'st viaxillcE are very much reduced in the parasitic 
Crustacea. In the present form they appear as a pair of 
minute palp-hke organs, situated laterally on the flaring base 
of the proboscis. 

The second maxillce are well developed, and appear as a 
pair of long, slender-jointed appendages arising posterior to 
the second antennae. Their free extremities are seen to be 
provided with hooks, while a pair of suckers will be found 
between their points of attachment. 

The niaxillipeds are considerably larger, directed poste- 
riorly rather than laterally, and bear, at their free ends, a 
peculiar attachment organ. Behind the maxillipeds are four 
pairs of S7vinvni7ig appendages^ of which the first are some- 
what reduced. Note the median sucker, between the first 
and second pair of swimming feet. 

The body is terminated below by a flap-like segment that 
bears a pair of laterally projecting styles. Compare with 
Cyclops, 

The greatly elongated egg-strings will be found to take 
their origin laterally from a point midway between the 
dorsal and ventral terminal flaps. 

Make drawings of the ventral surface and of the several 
appendages. 

Nauplii, the free -swimming young of many Crustacea, 
may be secured from the present form and in large num- 
bers. Tease one of the egg-strings and place its contents 
under a compound microscope. Each Nauj)lius will be 
found to bear three pairs of jointed appendages, which repre- 



lOO Invertebrate Zoology, 

sent the first and second ante^ince and the mandibles of the 
adult. Are the appendages biramous ? Is the body of the 
NaupUus segmented? Are there posteriorly directed ter- 
minal styles ? Is there a median ocellus ? Can you trace 
out the alimentary tract? 

Make a drawing of the Nauplius. 



A Cirriped Crustacean, loi 



A CIRRIPED CRUSTACEAN 

{Lepas fascicularis) . 

External Anatomy. — The highly specialized animal is 
attached at its anterior end by an elongated peduncle , and is 
protected laterally by a mussel-like shell. Of how many 
pieces does the shell consist? Do you find an elongated 
opening between the two halves of the shell ? The opening 
is on the ventral side. The meBian, dorsal piece of the 
shell is the carina, while lying laterally are the more pos- 
terior terga and the more anterior and ventral scuta. The 
scuta join in the mid- ventral line. From the ventral open- 
ing the six pairs of biramous appendages are thrust out for 
the securing of food. 

Draw the animal as seen from the right side, naming the 
parts. 

Stretch apart the valves and note that the integument of 
the animal, externally indurated with lime, passes, within 
the ventral opening, into a more delicate transparent fold, 
which completely separates the soft parts of the animal 
from the exterior. Note in particular the deeply lying 
oral cone^ the attachments of the biramous appendages, 
the aborted abdomen, and the greatly elongated intro- 
7?iittent organ, which occupies a position just back of 

^ The oral cone is a large knob-like mass which is made up of the 
mouth-parts, and bears, at its apex, the mouth. 



102 Invertebrate Zoology, 

the last pair of thoracic appendages.-^ Do you find the 
anus ? 

Remove and make a drawing of one of the appen- 
dages. 

Before the body has been opened, the transparency of the 
integument permits the location of several internal organs. 
A large dark-colored area on either side, near the base of 
the cone, marks the position of the " hepatic glands.''^ A 
smaller, orange-colored area near the base of the most 
anterior filament is the anterior end of the vas deferens. 
On the ventral side the muscular apparatus and the gan- 
glionic chain are beautifully shown. 

Carefully remove the right half of the shell, and trace 
the folds of the integument into the peduncle. The pedun- 
cle is a prolongation of the head, the anterior {first) anten- 
nce of the larva having entered into its formation.^ The 
second antennce are, in the adult, aborted. 

At the summit of the oral cone a large transverse fold will 
be found to bound the mouth anteriorly and to bear at each 
end a triangular "scale-shaped " piece. The mandibles and 
fi,rst maxillce bound the mouth laterally, while the second 
maxillce are partially fused and form a lower lip. Both 
mandibles and first maxillae have strong cutting edges. 

Digestive System. — Carefully opening the animal along 
the lateral Hne, note that a funnel-shaped tube leads from 

1 The abdomen is greatly reduced. It is represented on the dorsal 
side by a pair of small terminal flaps which cover the anal opening, 
while on the ventral side it supports the intromittent organ. 

2 The first antennae bear the so-called " cement glands," the secre- 
tion of which enables the larva to attach itself. In the adult these 
glands are to be found in the substance of the peduncle occupying a 
position in its dorsal portion. 



A Cirriped Crustacean. 103 

the 7notith to the short, straight oesophagus. The latter opens 
suddenly into a large stomach. Numerous dark hepatic 
glands will be seen on the walls of the stomach. The 
intestine is a straight tube of uniform size, extending from 
the stomach to the anus.^ 

Make a drawing of the alimentary tract as seen from the 
side. 

Excretory System. — Glandular bodies, possibly excre- 
tory in function, have been described as opening from the 
second maxillee. The ce??ient glands of the first antennae 
may also belong to the category of excretory organs. 

A closed Circulatory System is not present in the Cirri- 
pedia. Near the base of the oral cone, on either side of the 
animal, five elongated filaments are to be noted. These 
organs are probably respiratory in function. 

The Muscular System is developed chiefly for the 
movement of the divisions of the shell, the waving of the 
appendages, and the retraction of the soft parts. The young 
(Nauplii) are active swimmers. 

The arrangement of the muscles that move the mouth 
parts can often be seen through the transparent integument 
of the oral cone. 

The Nervous System. — Remove the stomach and 
intestine from the opening already made in the side of the 
animal. The nervous system occupies, as a chain of ganglia, 
a median ventral position. Anteriorly it surrounds the 
oesophagus {oesophageal ring or collar), and unites with the 

^ On either side of the rL'Sophat^eal end of the stomach is a whitish 
glandular organ, which may be called the " pancreas." 



104 Invertebrate Zoology, 

supra-cesophageal ganglion, from which nerves pass to a pair 
of minute, pigmented eye-spots. 
Draw. 

The Reproductive System. — The barnacle is hermaph- 
rodite. The ovaries will be found in the peduncle, the ova 
appearing as a collection of minute spheres loosely held 
together. The oviducts pass from the ovaries to the bases 
of the anterior thoracic appendages, and are difficult to 
follow.^ 

The testes may be seen through the transparent integu- 
ment of the body and appendages. Each gland, in alcoholic 
specimens, appears as a racemose structure of pale yellow 
color, the lobes extending from a larger antero-dorsal mass 
into the more anterior thoracic appendages, and into the 
filaments. 

If the six pairs of thoracic appendages be spread apart, the 
vasa defe7'entia will be observed entering the base of the 
intromittent organ. These ducts will be found to lead from 
the anterior end of the testis and to unite in the penis and 
form a common ductus ejaculato7ius. 

Make a drawing of the reproductive system. 

1 The opening of the oviduct is on the anterior surface at the point 
where the appendage joins the body. 



A Bracliyuran Crustacean. 105 



A BRACHYURAN CRUSTACEAN 
( Cancer irroratus) . 

External Anatomy. — Are the cephaloihorax and ah- 
doitien built upon a new plan, or is the plan presented by 
the lobster again adopted ? Which region of the body has 
been specially elaborated ? The abdomen of the female is 
much wider than that of the male ; to which sex does the 
specimen belong? 

Count the abdominal appendages of a female, and see if 
they agree with the same of the lobster. Count the same 
of the male. Why are there more appendages on the abdo- 
men of the female than on that of the male? (Examine 
a specimen that bears eggs.) Is the number of abdomi- 
nal somites different in the two sexes? Does the male show 
any traces of coalescence of abdominal segments? How 
does the number compare with the abdominal segments of 
Ho mams ? 

Is the number of ambulatory appendages the same as in 
the lobster? The number of appendages bearing pincers? 
In what main feature does the carapace differ from the cara- 
pace of the lobster? Do you find the homologue of the 
rostrum ? The transverse groove is more clearly shown in 
many related forms. Can you easily follow the groove to 
the margin of the carapace? Is this a free margin, as in 
Homarus ? Note the opening at the base of the first am- 
bulatory appendage, through which the water enters to bathe 



io6 Invertebrate Zoology. 

the gills. Do you find the external openings of the oviducts ? 
Of the vasa deferentia ? 

Draw the animal as seen from above. 

Remove the lower portion of the left thoracic pleuron, 
and expose the bases of the appendages. Podohranchice 
and arthrobraiichice are not present. Are there flabella at 
the bases of the ambulatory appendages ? 

Carefully remove the third maxilliped of the left side. 
Compare it with the same of the lobster. 

Draw. 

The second maxilliped will be found to have endopodite, 
exopoditCy and flabellwn, of the same general structure as in 
Homarus, Only two gills are present. 

Draw. 

The first maxilliped is foliaceous and gill-less. Note its 
greatly elongated flabellumy which extends far back into the 
branchial chamber. 

Remove the appendage and draw. 

Examine the right (uninjured) side, and see if you do 
not find at the base of the first maxilHped, and extending 
anteriorly, a large opening that leads from the branchial 
chamber. 

The second maxilla, as in the lobster, has a specially de- 
veloped flabellum for bailing the water out of the branchial 
chamber. Note how its protopodite is divided almost pre- 
cisely as in Hoinarus, The rudiment of the endopodite is 
especially interesting. 

Draw. 

Remove \ht first maxilla and draw, and do the same with 
the mandible. 

Examine the antennce^ and see which are first and which 
second. 



A Bmcliyuran Crustacean. 107 

Remove the second antenna. Do you find the elongated 
filament that was specially developed in the lobster? Can 
you find the openings of the green-glands ? 

Draw a second antenna. 

Carefiilly remove the first antenna. Find the position of 
the auditory sac. Do you find the representatives of the 
terminal filaments oi Honiarus? Which filament is provided 
with numerous sensory hairs ? 

Draw. 

Do the cojnpound eyes differ from the same of the lobster? 

Draw. 

Without injuring the gills, remove the right branchial 
wall. Pleurobranchia: will be found on the fifth and 
sixth thoracic segment ; a7'tJirobra7ichicE, one on the sec- 
ond, two on the third, and two on the fourth ; while 
podobranchice are found only on the second and third 
thoracic segments. 

Remove one of the gills, and see how its structure differs 
from that of the gill of the lobster. 

Internal Anatomy. — Carefully remove the dorsal por- 
tion of the carapace. Cut away the underlying integument, 
and expose the viscera. Cover the specimen with water, 
and, without displacing or injuring the organs, note as fol- 
lows : — 

The heart and its two pairs of cardiac apertures or 
valves; the pericardial sinus ; the openings into the sinus of 
the branchio-cardiac canals; the ophthalmic artery; the 
antenna ?y artery; the hepatic artery; xhQ superior abdom- 
inal artery. 

Somewhat anterior to the heart lies the stomach. Com- 
pare with Ho mar us. Note the arrangement of the dorsal 



io8 Invertebrate Zoology. 

gastric muscles. The lobes of the liver, or mesenteric gland, 
extend laterally until they reach the limits of the shell. 
Each lobe, as in the lobster, is composed of a multitude of 
tubules. 

Lying anteriorly to the heart, and extending laterally over 
the mesenteric gland, are the voluminous sextial organs. 
The testes appear as a coiled filament, extending from 
near the lateral walls of the stomach to the lateral angles of 
the shell. In the region of the pyloric end of the stomach 
the filament enlarges into a coiled duct, the vas deferens. 
Expose the green-glands, and trace out their ducts. 

The comparison of the nervous systein of the Brachyuran 
with that of the Macruran (Homarus) will prove most in- 
teresting. 

Draw the animal as seen from above. 



Alt Aniphipod Cnistacean. 109 



AN AMPHIPOD CRUSTACEAN 

( Talorchestia longicornis) . 

External Anatomy. — Select a large male specimen. 
(The males are generally larger and have antennae which 
almost equal the body in length.) Note the laterally com- 
pressed body and the numerous jointed appendages. Dis- 
tinguish between the hcad^ the thorax^ and the abdomen. 

Projecting anteriorly from the head are the smaller first 
aiitenncB. How many joints has each? Immediately be- 
neath the first antennae are the long second antennce. Of 
how many joints does each consist? Compare with the 
same organs of the female. 

Remove the head and examine from the side. Are there 
any suture-like lines that might lead one to suppose that 
the head is really composed of several fused segments? 
Note the lobe-like upper lip or lahrum. In what plane 
does it move? Is there a somewhat similar organ (the 
united first maxillipeds) , covering the mouth-parts from 
behind? 

Remove both labrum and the fused maxillipeds. The 
remaining mouth-parts move laterally. 

Lying immediately anterior to and under the maxillipeds 
are the second maxillce. Each is a delicate, foliaceous, 
bilobed organ, and bears numerous sctce along its free 
edge. 



no Invertebrate Zoology, 

Remove the second maxillae, and expose the more rigid 
bilobed first maxillce. The large, irregular Jaws work 
between the first maxiilce and the labrum. 

Open the jaws and note the opening of the 7nouth, 

Make drawings of the several appendages of the head. 

The first thoracic segment, bearing the first maxillipeds, 
has, as already noted, become fused with the head. The 
second thoracic segment bears a pair of fair-sized second 
maxilhpeds, while the third, homologous with the third max- 
illipeds of the lobster, bears a pair of enormous chelce. 
Behind the chelae are five pairs of ambulatory appendages 
supported on as many separate thoracic rings. 

Note the expanded coxal joints of the thoracic append- 
ages, the epiffieral plates. Spread the appendages apart, 
laterally, exposing the gills. Each gill arises from the pos- 
terior side of an appendage, near where the latter is inserted. 
How many gills are there? Do you find the same number 
in the female ? In the latter do not confuse the gills with 
the oostegites, or lamellar plates, which form the brood-pouch. 

Attached to the anterior part of the abdomen are three 
pairs of swimming-feet, while the posterior portion bears the 
same number oi jmnping-feet. Are there six separate seg- 
ments bearing the six pairs of appendages ? Note the small 
terminal plate. Are all the abdominal appendages biramous ? 

Digestive System. — Remove the appendages from a 
large specimen, and, after opening along the mid-ventral 
line, pin the animal out under water or alcohol, and wash 
any cloudiness away. 

The short oesophagus will be found to lead into a somewhat 
rounded crop, from which extends, posteriorly, the straight 
intestine. The hepatopancreatic coeca appear as four elongated 



All AvipJiipod Criistacea7i. in 

sacs extending from their attachment at the anterior end of 
the intestine, two-thirds the length of the body. How are they 
held in place? Does the anus open dorsally or ventrally? 
Draw. 

Excretory System. — A pair of small, somewhat coiled 
diverticula, the 7neseuteric tubules^ are to be seen lying along 
each side of the more posterior portion of the intestine. 
Trace out their course and see where they open into the 
intestine. The external openings of the antennal glands 
may be observed, near the median ventral line, as two small 
pores, each on the basal joint of a second antenna. 

Draw, as seen from the side. 

The Reproductive System. — The testes are to be 
observed as a pair of delicate tubes lying longitudinally, 
immediately above the middle portion of the intestine. 
Follow both to their external openings. Are the testes in 
the thoracic or in the abdominal cavity? 

Draw. 

The ovaries occupy a position similar to that of the testes. 
The openings of the oviducts may be found at the bases of 
the fifth pair of appendages. Each is a small pore between 
the gill and the oostegite. 

Draw. 

The Circulatory System. —The heart wAW be found as 
a delicate elongated sac lying along the dorsal part of the 
thoracic cavity. The blood enters the organ through cer- 
tain lateral ostia and is then forced, through anterior and 
posterior aortce^ into the various lacunar of the body. The 
blood finally reaches \}c\^ gills, situated, as has been observed, 
on the thoracic segments. It is from them returned to the 
heart. 



112 Invertebrate Zoology. 

The Muscular System. — The Amphipods are active 
jumpers. Observe the strong extensor muscles of the tail. 
Determine also the general arrangement of the muscles 
which move the appendages. 

The Nervous System. — What is the position of the 
compound eyes ? Are they stalked ox sessile ? Certain spec- 
imens clearly show, through the transparent sterna of the 
thorax and abdomen, the ventral ganglionic chain. Is it 
clearly made up of two strings? Do you find longitudinal 
and transverse commissures ? Do nerves leave the ganglia ? 
Does the number of gangha correspond to the number of 
segments? Carefully dissect in the region of the head, 
noting the infra- and sicpra-oesophageal ganglia and the 
oesophageal ri7ig or collar. 

Make a drawing of the nervous system, naming all the 
parts. 



The King Crab. 113 



THE KING CRAB 

{Limichcs polyphemus). 

External Anatomy. — Note, on examining the animal 
from above, that the chitinous shell is divisible into a large 
anteriorly lying cephalolhorax and a smaller, polygonal ab- 
domen, terminated posteriorly by a rigid caudal spine. 

The cephalothorax bears a pair of lateral, compound eyes, 
and a pair of median ocelli. The latter occupy positions, 
one on each side of the frontal spine. 

Is there anything on the dorsal surface of the abdomen 
that would show that it might possibly be made up of sev- 
eral fused segments or 77ietameres ? How many movable 
spines are there along the margin ? How many pairs of pits 
each side of the median line ? 

Draw. 

Examining the lower, concave surface of the specimen, 
observe the seven pairs of cephalothoracic limbs. The first 
{chelicerce) , smaller than the remaining, are followed in 
immature specimens and in females by four pairs of pincer- 
bearing legs. Do the pincers open and close as in Homa- 
rtcs ? The sixth pair of appendages are directed posteriorly. 
Have they anything that might be of assistance in forcing 
the animal through the mud? Note the exopodite-like 
process at the base of each. 

The chilaria are supposed by some to represent a pair 



114 Invertebrate Zoology, 

of appendages. They are small unjointed processes lying 
between the bases of the pair of appendages just considered. 

The seventh pair of cephalothoracic appendages are con- 
siderably modified and form the operculu7n or cover for the 
abdominal appendages. The two are united in the median 
line. Certain transverse lines mark their lines of original 
segmentation. 

The motcth opens in the median line between the bases of 
the four pincer-bearing appendages. In front of it is a coni- 
cal elevation, the upper lip. 

The abdomen bears five pairs of modified appendages, each 
pair resembling the operculum, and covering the large gill- 
books. By the movement of the abdominal appendages and 
the gill-books the animals can slowly swim through the water. 
, At the base of the caudal spine the opening of the antes 
will be observed. The external openings of the genital organs 
will be found on the posterior surface of the operculum. 
The external openings of the coxal glands have been found 
in embryos on the basal joints of the fifth pair of cephalo- 
thoracic legs. 

Internal Anatomy. — With a strong knife remove the 
entire upper portion of the shell of both cephalothorax and 
abdomen. 

The Muscular System. — The ^Xxong flexor muscles will 
be seen to have a longitudinal course along each side of the 
median plane. The muscles which move the legs are dis- 
posed laterally to the flexors, and their fibres are arranged, 
for the greater part, dorso-ventrally. 

The Circulatory System. — Along the mid-dorsal line, 
just below the flexor muscles, the elongated heart will be 



The King Crab, 115 

found. It extends from a point under the median eyes to 
the posterior half of the abdomen. It has, extending ante- 
riorly, a frontal artery which divides into a right and a left 
anterior marginal artery} The marginal arteries bend out- 
wardly, laterally, and posteriorly, following the curve of the 
margin of the cephalothorax. T\\q posterior marginal arte- 
ries are the abdominal continuations of the anterior marginals. 
Extending laterally from the heart are the lateral arteries. 

The "aortic arteries''' take their origin from the anterior 
end of the heart, and pass, one on either side of the oesopha- 
gus, to the ciraim-oral reseriwir, below mentioned. 

TYi^ first latej^al arteries branch off from about the middle 
of the cephalothorax ; the second and third latei^al arteries, 
from the posterior portion of the cephalothorax. From the 
second, branches communicate with the marginal arteries 
and with the hepatic a7^teries. The latter lie parallel to the 
anterior marginal, and supply blood to the liver. 

The collateral arteries lie longitudinally, one on each side, 
parallel to the heart. They connect the several lateral arteries. 

The heart is continued posteriorly by the superior abdomi- 
nal artery. 

Branchial arteiHes pass from the abdominal collaterals to 
the gills. 

The arteries of the ventral side cannot be now dissected. 
They enclose the nervous system and consist of a circu7n- 
oral reservoir, from which the crural arte7ies are given off 
to the legs. Extending posteriorly from the reservoir is 
the ventral artery, which gives rise to branchial and a7ial 
branches. 

The blood is returned from the gills and all parts of the 

1 The frontal artery extends anteriorly to the margin of the cephalo- 
thorax before dividing into the marginal arteries. 



ii6 Invertebrate Zoology, 

body, through certain irregular channels, to the pericardial 
sac, from which it passes into the aorta through a series 
(eight pairs) of ostia. 

Make drawings illustrating the course of the heart and 
principal blood-vessels. 

The Digestive System. — Remove the heart and expose 
the more ventrally lying ahmentary tract. The mouth will 
be found to lead into an anteriorly and upwardly directed 
(Esophagus which opens into a strong- walled anterior stomach 
or crop. Cut the crop open and note the character of its 
hning. The crop opens posteriorly into a thin-walled stom- 
achy which extends, without any remarkable change, to the 
short proctodcEum or rectum^ the latter opening to the ex- 
terior through the anus. 

Carefully open the stomach and note the entrance of the 
bile-ducts. These bile-ducts lead from the voluminous liver, 
which nearly fills the cavity of the cephalothorax. 

Make a drawing of the digestive system. 

The Reproductive System. — The sexes are separate. 
The ovaries or testes form a network of tubes which ramify 
over and through the substance of the liver. Their ducts 
may be traced to the external openings already noted. 

The Excretory System. — The coxal glands He along 
both sides of the stomach, each consisting of a longitudinal 
portion, from which project laterally four finger-shaped 
lobes. In Hfe they are " brick-red " in color. The func- 
tion of these organs is not definitely known. 

Draw. 

The Nervous System. — Remove the alimentary tract 
from the beginning of the crop to the anus, and expose, 



The King Crab. 117 

immediately under the stomach, the cartilaginous sternal 
plate. Note the outline of the plate and remove it with 
care, as a portion of the nervous system lies immediately 
beneath. 

The nervous system consists of a brain, a circum-oral ring, 
and a ventral, posterior continuation, the ventral cord. The 
brain is a rounded body lying in front of the oesophagus. 
Trace the nerves leading from it. The circum-oral ring is 
a flattened disc which innervates the ambulatory appen- 
dages. The posterior part of the ventral cord gives off 
branches to the abdominal appendages. The more central 
portions of the nervous system are surrounded by a blood- 
sinus. 

Make a drawing of the nervous system. 



Ii8 hivertebrate Zoology. 



AN ARACHNID 
{^Epeira riparia). 

External Anatomy. — The body is here again divided 
into a cephalothorax and an abdome?i, the two being united 
by a small peduncle. The cephalothorax is flattened above 
and bears six pairs of appendages. The most anterior pair, 
the chelicerce, are provided with strong cutting jaws and are 
pierced, near their tips, by a small opening which leads from 
di poison-gland. They lie anterior to the mouth. 

ThQpedipalps, which lie immediately behind the chelicerae, 
and on each side of the mouth, are more leg-like. They 
consist of a strong-bodied, basal portion and of an elongated, 
many-jointed y^<?/<fr ox palpus. In the males the palpi are 
specialized into organs for bearing the spermatophores. 
Compare this pair of appendages with the same of Limulus. 

The four pairs of legs take their origin from behind the 
mouth, along the lateral portion of the cephalothorax. Do 
they all agree in having the same number of joints? Note 
the hook- like organ terminating each. 

Examining the abdomen from above, do you find any- 
thing (grooves or transverse bands) that might suggest that 
it was once segmented ? 

The lower surface of the abdomen presents several organs 
of interest. — The external openings of the lung-sacs appear 
as two transverse slits, one on either side of the anterior por- 
tion of the abdomen. In the median line, between them, is 



Aji Arachnid. 119 

the external opening of the sexual organs^ in the female 
highly elaborated. The spinnerets will be found at the pos- 
terior end of the abdomen as three pairs of papillae. They 
are jointed, and probably represent specialized abdominal 
appendages. The smaller middle pair of spinnerets are 
covered by the much larger anterior and posterior pair, 
while the anal papilla is closely folded against the latter 
as a transverse chitinous elevation. If the anal papilla is 
pressed back, the opening of the anus will be found. 

A small pore, or spiracle, lying in the median line, imme- 
diately in front of the spinnerets, leads from a series of 
branched abdoj7ii7ial trachcce. This pore is often difficult to 
find. It lies just in front of a thorn-like process which rests 
just between the first pair of spinnerets. If the integument 
at this point be carefully picked away, the tracheae will be 
found. 

]\Iake a drawing of the spider as seen from above, and 
another as seen from below. 

Internal Anatomy. — Carefully remove the integument 
from the upper half of the thorax and abdomen. 

The Circulatory System. — The heai-t is an elongated, 
thin-walled tube which extends along the dorso-median por- 
tion of the abdomen and is continued anteriorly, as the ante- 
rior aorta, through the peduncle, into the cephalothorax. 
The heart is really enclosed in a very delicate pc7'icardiu7n, 
which holds the blood as it is returned from the lacunce of 
the body, finally pouring it into the heart through certain 
lateral ostia. The blood, leaving the heart through the ante- 
rior and posterior aort^, is conveyed in arteries for only a 
short distance. It soon enters lacunas and sinuses, in which 
it pursues a definite course until it gathers in a large reservoir 



I20 Invertebrate Zoology. 

near the lung-sacs. In the lung-sacs it is purified, and from 
thence passes directly to the pericardium. 

The Reproductive System. — The ovaries of the female 
often nearly fill the abdominal cavity, the ova being very 
irregular in outline, as a result of their mutual pressure. 
The oviducts may be traced to the external opening already 
noted. Lying on either side of the external opening is a 
coiled tubular organ, the receptaculum seminis, that receives 
the spermatophore of the male, and retains the spermatozoa 
until the time of egg-laying. The testes of the male are 
elongated tubular glands, which lie longitudinally along the 
lower portion of the abdominal cavity. Before opening to 
the exterior each gland is continued into a coiled vas 
deferens} 

The Digestive System. — The straight intestine will be 
found to He immediately under the heart and to give off lat- 
erally several coecal diverticiUa. Followed posteriorly, the 
intestine opens into an enlarged rectum^ which also receives 
the ducts from certain many- branched tubes, the Malpighian 
vessels. 

Followed anteriorly, the intestine passes through the 
peduncle and enlarges within the cephalothorax into a 
stomach. From the stomach, coecal diverticula extend out 
as loops into the bases of the legs. Certain gastric muscles 
are so arranged that they can enlarge the central portion of 
the stomach, which thus acts as a sucking-organ. 

The oesophagus may be followed as a tube leading from 
the mouth to the stomach. 

^ The spermatic fluid is collected in the pedipalps and retained in 
spermatophores until transferred to the receptacula of the female. 



A71 Arachnid, 121 

T\it poison-glands^ which are probably modified salivary 
glands, will be observed in the anterior portion of the cephalo- 
thoracic cavity, immediately over the chelicerae. Trace 
their ducts to the terminal openings already noted. 

Make an imaginary drawing of the viscera, thus far studied, 
as they would appear in side view. 

Carefully remove the digestive tract and note, lying imme- 
diately below it in the cephalothorax, the " diaphragm," a 
thin sheet of tissue extending horizontally almost entirely 
across the cavity. Recall the sternal plate of Limulus. 

The Respiratory System. — The external openings of 
the lung-sacs have already been noted. Each lung-sac con- 
tains a cavity into which a series of lamellcE, like the leaves 
of a book, project. In these thin-walled lamellae the blood 
circulates and is purified. Recall the gill-books of the king 
crab. 

The spiracidar opening of the tracheal system of air-tubes 
has been already noted. The arrangement of the ti'achece 
or air -tubes is much as in insects. It is through them that 
the air is conveyed to many of the tissues. 

The silk glands. In the abdominal cavity, immediately 
over the spinnerets, the silk glands will be observed. Each 
gland is composed of a brush of tubular organs of which the 
more anterior are the larger. 

The Nervous System. — The brain or supra-cEsopha- 
geal ganglion occupies a position in front of the oesophagus 
and innervates the ocelli and the chelicerae.^ The oesopha- 

^ The arrangement of the oceUi is different in different species. In 
the present type two pairs of median ocelli form a quadrant, while a pair 
of lateral ocelli will be found on elevations just above the Imse of each 
chelicera. 



122 Invertebrate Zoology. 

geal collar connects the brain with a large thoracic ganglionic 
mass from which nerves extend to the lateral appendages 
and into the abdomen. 

Finish the drawing already begun, representing the dia- 
phragm, lung- sac, tracheae, silk glands, and nervous system. 



A Lepidopterous Insect. 123 



A LEPIDOPTEROUS INSECT 

{Sphinx sp,). 
Larval Stage. 

External Anatomy. — The body of the larva or cater- 
pillar is elongated and vermiform and, Hke that of Arthro- 
pods already studied, is made up of serially arranged seg- 
ments or metameres. 

The head bears, anteriorly and laterally, a pair of large, 
convex parietal plates which meet above in the median line 
and enclose, lower down, a smaller, median, triangular /r^/^/Vz/ 
plate. The ocelli are found as a series of pigmented dots at 
the lower anterior portion of each parietal plate. How 
many ocelli are there ? 

The first pair of cephalic appendages, the antenitcE, take 
their origin from the lower anterior angles of the parietal 
plates. Each antenna is made up of several joints. 

The opening of the month will be found midway between 
the antennae. It is bounded anteriorly by a two-lobed upper- 
lip or labrum, and laterally by a pair of strong chiXmons Jaws 
or mandibles. In what plane do the mandibles move ? 

The maxillce lie immediately posterior to the mandibles. 
Each is provided with a small jointed organ, \hQ palpus. In 
the median line between the maxillse is the cone-shaped 
lower-lip or labium. It bears the external opening of the 
duct leading from the silk-glands. 



124 Invertebrate Zoology, 

Make drawings of the head as seen from the side and from 
below. 

The segments immediately following the head, the pro-, 
meso-y and meta-thoracic, are each provided with a pair of 
jointed appendages, the thoracic legs. 

Behind the thoracic region, the abdoinen extends as a 
series of ten segments. Do the first two abdominal seg- 
ments bear appendages? The fleshy appendages of the 
third, fourth, fifth, and sixth abdominal segments are called 
the prolegs. Note that each is terminated at its free end by 
a series of hooks. The seventh and eighth segments are 
not provided with appendages, though the eighth frequently 
bears a median dorsal spine. The ninth segment is short 
and somewhat suppressed, while the tenth is pierced by the 
anus and bears a pair of anal prolegs. In the embryo all 
the abdominal segments are provided with rudimentary 
appendages. 

Extending along each side of the animal are a series oi spir- 
acles, openings which lead within the animal into an elabo- 
rate system of branched respi?^atory tubes or trachecE, The 
spiracles do not occur on every segment, but are present 
upon the first thoracic and upon all the abdominal segments 
except the ninth and tenth. 

Make a drawing of the animal as it appears when viewed 
from the side. 

Internal Anatomy. — With a fine pair of scissors cut 
through the integument, along each side of the animal a little 
above the line of spiracles, from the side of the head to the 
ninth abdominal segment. Remove the dorsal piece without 
disturbing the underlying viscera. 



A Lepidopteroiis bisect. 125 

The Circulatory System. — The heart w'^ be observed 
as a median tube extending along the mid-dorsal Hne of the 
animal, immediately below the integument. The bloody 
which contains amoeboid corpuscles, enters the organ through 
certain lateral ostia, and is forced anteriorly, where it enters 
the aorta, from whence it is distributed to the various 
sinuses of the body. 

The Muscular System. — Many parallel bands of mus- 
cles, segmentally arranged, will be observed immediately 
under the integument. In the head they become specially 
developed in the neighborhood of the mouth parts. 

Remove the heart and the laterally lying muscle bands. — 
The body-cavity will be found to be apparently filled with the 
subdivisions of \ht fat-body, though more careful examination 
with a lens will reveal the presence of other organs of some- 
what the same appearance.^ 

The Digestive System. — The mesenteron or stomach 
will be observed as a large, rather thick-walled cylinder extend- 
ing antero-posteriorly through the body-cavity. Followed 
anteriorly, the stomach is found to lead from a thinner- walled 
oesophagus. Posteriorly, the stomach becomes abruptly con- 
stricted and passes into the intestine, which in turns opens 
through the rectum to the exterior. The salivary glands will 
be found lying anteriorly, along the sides of the oesophagus. 
Their ducts open into the mouth. Associated with the sali- 
vary glands are the silk glands or serictaria, a pair of elon- 
gated organs which may be found lying side by side along 
the lower surface of the anterior portion of the mesenteron.^ 

^ The substance of the fat-body is loose and flocculent. 
2 Both salivary and silk glands are elongated tubular organs. Each 
salivary gland extends as a coiled thread from the dorsal region of the 



126 Invertebrate Zoology, 

The external opening of the silk glands has already been 
noted. 

Make a drawing of the alimentary tract. 

The Excretory System. — A series of irregular tubes 
will be observed lying upon the posterior half of the mesen- 
teron, each pursuing a somewhat irregular course and pre- 
senting, when seen under the lens, a beaded appearance. 
These organs are the Malpighian tubes, six in number. Each, 
after pursuing a tortuous course, empties into the intestine. 

Make a drawing of the excretory system. 

The Respiratory System. — The spiracular openings 
have already been noted. Each leads into a series of branch- 
ing tubes, the trachece, which subdivide into very minute 
subdivisions, carrying the air to the most remote tissues. 
The tracheae are lined with chitin and are strengthened by a 
spirally coiled chitinous ridge. 

third thoracic or first abdominal segment along the lateral surface of 
the anterior portion of the digestive tract, in its course being partly 
covered by the lobes of the fat-body. 

The salivary duct passes down the posterior surface of the bundle 
of muscles that works the jaws. 

The silk glands are much larger than the salivary glands and occupy 
a very different position. Their ducts lie immediately below the oesopha- 
gus and the anterior portion of the stomach. The greater portion of 
each gland appears as a coiled cord, more or less surrounded by the fat- 
body and lying on a level with the spiracular openings, in the middle 
and posterior portions of the body-cavity. 

The salivary and silk glands should not be confused with the much 
more delicate Malpighian tubes, which are arranged in more nearly 
parallel lines along the outer surface of the stomach. 



A Lepidopteroiis Insect. 127 

The Reproductive System. — The sexual glands are 
somewhat difficult to find in alcoholic specimens. They lie 
in the fifth abdominal segment, immediately beneath the 
dorsal integument. In favorable specimens a delicate duct 
may be traced from each, around the intestine, to the lower 
side of the body- cavity. 

The Nervous System. — The nervous system has the 
same general disposition that has already been noted for 
related Arthropods. The brain will be found far for- 
ward, immediately over the mouth, and uniting with the 
infra- (Esophageal ganglion through the cir cum- oesophageal 
collar. 

From the brain, which is divided into a right and a left 
half by a median furrow, nerves may be traced to the ocelli, 
antennae, and to the oesophagus. 

^\it first or infra- oesophageal ganglion innervates the man- 
dibles, the labium, and the silk glands, and by its two con- 
nectives unites with the next following ganglia. 

The second ganglion is of relatively small size. It inner- 
vates certain muscles of the head and neck and the first pair 
of legs. 

The third ganglion innervates the second pair of legs, while 
\htfou7'thganglio7i supplies the third pair. 

The abdominal ganglia are seven in number, — the first 
abdominal segment bearing the fifths the second segment 
the sixth, the third segment the seventh, the fourth segment 
the eighth, the fifth the ninth, the sixth the tenth, and the 
seventh the eleve^ith ganglion. The eleventh ganglion is, 
moreover, clearly divided into an anterior and posterior half, 
and is, hence, probably composed of two fused ganglia. 



128 Invertebrate Zoology. 

There are no nerve-centres in the remaining abdominal 
segments. 

While the connectives leading from the second to the 
third and from the third to the fourth gangha are free and 
form loops, those leading between the remaining ganglia 
are more or less miited together. 

Make a drawing of the dorsal view of the nervous system. 



An Orthopteroits Insect. i2g 



AN ORTHOPTEROUS INSECT 

{Acridium americanuni). 
Adult Stage. 

External Anatomy. — Observe that the three divisions 
of the body, head, thorax, and abdomen, are here much 
more definitely outlined than they were in the caterpillar. 

The head bears a pair of antenncE, each made up of sev- 
eral joints ; a pair of large compound eyes ; a median and 
two lateral ocelli; a bilobed labruni or npper-lip ; a pair 
of strong mandibles or jaws which move laterally ; a pair of 
maxillcB lying immediately behind the mandibles, and each 
bearing a lateral, jointed apparatus, the palpus ; and a 
bilobed lower-lip or labiicm, which lies posterior to the max- 
illae, and is also provided with palpi. As the mouth-parts 
are opened and the inouth exposed, the tongue will be 
noticed as a chitinous papilla on its floor. 

The thorax has the same segments that were present in 
the caterpillar. The prothorax is the largest of the three 
and bears the first pair of legs. Its tergum or dorsal por- 
tion is enlarged and forms a shield. The me so- and meta- 
thorax are somewhat united together. The mesothorax 
bears the second pair of legs and \h^ first pair of wings, while 
the metathorax bears the much larger third pair of legs and 
second pair of wings. 

The legs will be found to consist of a series of joints and 
to be terminated by a pair of hook-like organs. The joints 



130 Invertebrate Zoology. 

of the legs are as follows : The coxa^ short and ring-like, 
bears at its free end the trochanter, which is a little smaller 
than the coxa, to which, in the third leg, it becomes fused. 
The trochanter bears a long joint, the femur, which, at its 
free end, bears another long joint, the tibia. The tarsus 
is made up of a series of small movable joints which bear 
pads on their lower surfaces. The tarsus is terminated by 
the claws. 

The fo7'e-wings or wing-covers differ from the true wings. 
Note the arrangement of their veins, the rib-like lines which 
strengthen them and which are in communication with the 
circulatory and tracheal system. The second or true-wings 
are, when at rest, folded like a fan. Note the arrangement 
of the veins and see if the wing-covers, when expanded, do 
not support the anterior edge of the true- wings. 

The abdomen is composed of a series of ten segments or 
metameres, all but the last two or three of which are very 
evident. There are no abdominal appendages. 

The first abdominal segment is somewhat modified from 
its association with the metathorax. Laterally, it is pierced 
by two large openings, one on either side, which lead into 
the auditory organs. The abdominal segments of the two 
sexes from the first to the eighth closely resemble each 
other. 

The ninth abdominal segment of the fe^nale is only about 
one-fourth as wide as the eighth, and is not provided with an 
independent sternal piece, the sternum of the eighth extend- 
ing to the posterior end of the mid-ventral line. The pos- 
terior edge of the tenth abdominal segment follows a line 
parallel with posterior edge of the eighth. There project 
posteriorly from the tenth segment a series of more or less 
flexible pieces of which the dorsal is the larger and may 



An Ortlwpteroits Insect, 131 

represent the tergum of an eleventh segment. This dorsal 
piece rests laterally upon a pair of triangular plates, the 
podical plates^ the lower edges of which follow the course 
taken by the lower edges of the ninth and tenth segments. 
Resting laterally upon the podical plates are short pointed 
processes, the ceixi. The ovipositor fills up that opening at 
the posterior end of the body, which is bounded by the free 
edges of the podical plates and the eighth sternal piece. 
The ovipositor is made up of two dorsal and two ventral 
pieces, all of which have sharp chitinous points. The anus 
opens between the dorsal pieces, and the oviduct between the 
ventral. 

The abdomen of the male is relatively smaller than that of 
the female. The ninth and tenth segments are provided with 
a common sternal plate. The podical plates are reduced, 
while the cerci are relatively larger. A subgenital plate lies 
below the podical plates and continues posteriorly the ven- 
tral series of sterna. 

Spiracles will be observed as follows : The most anterior 
is on the posterior edge of the prothorax, under the lateral 
fold of the shield-like piece. The second is at about the 
same level, behind the edge of the mesothorax. The third 
pierces the first abdominal ring just within the anterior mar- 
gin of the auditory organ. The seven succeeding abdominal 
rings are each provided with spiracular openings. Spiracles 
do not occur on the ninth and tenth segments. 

Internal Anatemy. — Carefully open the animal along 
the mid-dorsal line. 

The Circulatory System. — The heart will be found 
occupying the same place that it has occupied in many 
other Arthropods, and presents no remarkable features. 



132 Invertebrate Zoology. 

The Muscular System. — Lying either side of the heart 
are the longitudinal abdominal muscles » The thorax con- 
tains several bundles oi alary muscles. Are those which move 
the fore-wings separate from those which move the larger 
posterior wings ? Fat-bodies may be found forming a loose 
tissue throughout the cavity of the abdomen. 

The Respiratory System. — The external openings of 
the respiratory organs, or trachece, have been already noted. 
They will be found to lead, within the body- cavity, to a 
many-branched system of tubes which convey the air to the 
tissues, as has already been observed in the caterpillar. 

The Reproductive System. — The reproductive gland 
rests in the upper part of the abdominal cavity. The ovary 
is a bilateral organ which is continued posteriorly into a pair 
of oviducts. The oviducts pass to the lower side of the 
abdomen, where they unite and form the vagina. The vagina 
opens to the exterior between the ventral pieces of the 
ovipositor. Slightly above and anterior to the external open- 
ing of the vagina, the much smaller opening which leads 
from the bursa copulatrix will be found. The bursa is a 
small sac which receives the spermatozoa. It is situated 
beneath the rectum. 

The Digestive System. — The oesophagus leads into a 
large crop which extends from the mesothorax to the anterior 
part of the abdomen. Lying laterally to the crop are the 
branched salivary glands^ the ducts of which may be traced 
to their openings into the mouth. In the abdomen the crop 
opens into the stomach which extends over half the length of 
the abdominal cavity. The stomach opens into the intestine. 
The gastric coeca are a series of pouches which lie parallel to 



An OrtJiopteroiis Insect. 133 

the stomach and open into it. How many are there? The 
intestine is somewhat less than the stomach in size. It 
receives the ducts which lead from the Malpighian bodies. 
The latter appear as a tangle of minute tubes. The intestine 
opens into the rectum^ which in turn opens through the anus 
to the exterior. 

The Nervous System. — The brai?i occupies the same 
position that it has been found to occupy in all the Arthro- 
pods that have been studied. The cesophageal collar and 
ventral nerve-chain present no new features. Is there a 
ganglion for each thoracic segment ? There are five abdom- 
inal ganglia. In which segments do they rest? 



134 Invertebrate Zoology, 



A SIMPLE TUNICATE 

{Mo/gu/a manhattensis) . 

This species is quite abundant along the New England 
shores, attached to submerged stones and woodwork. 
Though occasionally solitary, the individuals are more often 
found in clusters of varying sizes. It is our most common 
Simple Tunicate, and is related to the Ciona so frequently 
mentioned in the European text-books. 

External Anatomy. — Though individual specimens 
vary, the more general shape of the present species is that 
of a two-necked flask, the larger neck or siphon serving for 
the entrance of water and food, the other, slightly smaller 
and often abruptly curved, serving for the escape of the 
strained water, the waste products of digestion and excre- 
tion, and also for the egress of the ova or embryos. The 
incurrent opening or month is surrounded by a series of 
circum-oral lobes or tentacles, which may be folded in such 
a way as to completely close the orifice. Are similar lobes 
arranged around the exciu^rent or cloacal opening? The 
outer surface of the animal has a felty appearance, due to 
the presence of innumerable papillce. The papillae entangle 
foreign matter, and thus the animal secures a protective 
coloring. In certain specimens the deeply colored vis- 
cera are to be seen through the semi-transparent body 
walls. 



A Shnple Tunicate. 1 35 

Note that the only plane that will divide the animal 
bilaterally passes through the long axis of each neck. Sub- 
sequent study will show that this plane actually separates 
the right from the left. The incurrent siphon arises from 
the morphological anterior end, while the cloacal tube 
extends from the posterior end. The shorter distance 
between the two is along the viid-dorsal line, while the 
greater distance marks the ventral line. Through the walls 
a light-colored band will be observed, extending along the 
anterior portion of the mid-ventral line. It is the endostyle, 
and, as subsequent dissections will show, lies along the floor 
of the pharynx. 

The outer covering of the animal, " tunic " or " test,'" 
should now be partially removed from the left side. This 
covering will be found to be thick and tough : its outer sur- 
face, except where the specimen was attached to others, 
rough and dirty ; its inner surface smooth and easily sepa- 
rated from the transparent underlying " 7?tantle.''^ 

The entire tunic may now be removed, and its only points 
of firm attachment to the underlying mantle are found at 
the margins of the incurrent and excurrent openings. 
Through the transparent mantle the contained deeply 
colored viscera are to be seen, while the mantle itself is 
found to be provided with certain clear white bands of 
muscle tissue. These muscle bands are especially abundant 
on the tubes, where they are arranged in longitudinal bundles 
and transverse fibi^es. How are they arranged on other 
parts of the mantle? It is through the activity of these 
muscles that the animals contract and forcibly eject the 
contained sea-water. The transverse fibres form sphinctei-s 
around the mouth and at the base of each siphon, and move 
the six oral and four anal flaps. 



136 Invertebrate Zoology, 

Internal Anatomy. — Viewing the specimen from the 
left side, the course of the S-shaped digestive tract may 
readily be followed. The tract is made up of two parallel 
portions, the oesophagus and stomach forming the lower 
limb, and the intestine forming the upper. Lying just 
above the, often dark-colored, intestinal loop is the light- 
colored sexual gland. The delicate sexual duct extends 
dorsally and posteriorly, parallel with the posterior section 
of the intestine. 

Lying deeper than the just mentioned viscera are six 
nearly parallel light-colored bands. They are the b^^anchial 
folds, and will be considered later on. 

At a point on the dorsal surface, about midway between 
the siphons, the ganglion will be observed as a small opaque 
spot. Notice the nerves, and, if possible, trace them to the 
siphon tubes. 

Again follow the course of the opaque endostyle. It ex- 
tends along the mid-ventral line, from near the base of the 
oral siphon to a point removed nearly 180°. Its posterior 
termination is near the point of origin of the oesophagus.^ 

Through the transparent mantle of the right side six 
branchial folds and a large sexual gland will be at once 
recognized. The duct leading from the sexual gland 
extends in a nearly horizontal direction towards the cloacal 
siphon. It often contains eggs or embryos. Lying parallel 
to and below the sexual gland, enclosed in a pericardium, is 
the heart, (In alcoholic specimens the circulatory system 
is not easily dissected.) Below (ventral to) the heart is a 
crescentic sac of considerable size. It is the r-enal organ, 
and often contains brownish flakes and concretions. 

^ The endostyle may be the homologue of the hypobranchial groove 
of Amphioxus, and of the thyroid gland of higher Vertebrates. 



A Simple T^micate, 137 

If the specimen is viewed from the dorsal side, a circular 
line will be found to extend from the anterior end of the 
endostyle around either side of the oral siphon to the 
ganglion. This line marks the position of the peripharyn- 
geal bajids. 

Drawings of the right and left side of the animal should 
now be made. 

By gently pressing upon the mantle it will be shown that 
there is a space between it and the deeper lying branchial 
bands. This space is the atj'ium or peribrajichial chamber, 
and can be beautifully seen if one now carefully removes the 
cloacal siphon by cutting around its base, beginning just 
above the ganglion. The cavity thus opened is actually the 
cloacal chamber, though the right and left halves of the peri- 
branchial chambers are seen to lead direcdy from it as we 
look down through the artificial opening. The branchial 
folds are now seen to form the longitudinal ribs of a reticu- 
lated sac, the branchial sac or phaiynx. Crossing the bands 
at right angles are certain transverse vessels, and stretched 
between vessels and ribs is a delicate membrane pierced by 
minute openings or stigmata. 

On the branchial sac a dorso-median line will be observ^ed 
to extend from near the ganglion to near the posterior end 
of the endostyle. The anal opening will be found near the 
lower end of this line. The intestine lies along the floor of 
the left peribranchial chamber, and is often deeply colored 
from the presence of contained faecal matter. The openings 
of the gefiital ducts are to be seen on the right and left 
external branchial walls respectively. The cloacal chamber 
receives then the waste products of digestion, the secretion 
of the sexual glands, and also the water which flows into it 
directly through the stigmata of the posterior wall of the 



138 Invertebrate Zoology. 

branchial sac as well as the water which flows from the two 
large laterally lying peribranchial chambers. 

Slit the mantle from the opening already made, along 
the upper edge of the left peribranchial cavity and thence 
ventrally along a line midway between the endostyle and 
the lower loop of the digestive tract, cutting through the 
strands or trabeculce that connect the mantle with the 
pharyngeal sac. The external wall may be now lifted and 
turned down and the extent of the left branchial chamber 
definitely established. On its external wall the exact course 
of the alimentary tract will be noted from the origin of 
the oesophagus at the point where the branchial bands con- 
verge, to the anus. Again note the transverse vessels and 
stigmata. 

In the same way as above directed open the right peri- 
branchial chamber and note the course taken by the sexual 
gland and renal organ. The two peribranchial chambers 
are not confluent along the ventral line. 

Passing the point of a fine pair of scissors into the oral 
siphon, carefully cut along near the ventral line of the 
branchial sac midway between the endostyle and the ventral 
branchial band. T\\t pharyngeal cavity will thus be opened. 
The twelve branchial folds converge from their origin, just 
below the peripharyngeal bands, to the opening of the oesoph- 
agus. Each lateral half of the peripharyngeal bands, tak- 
ing its origin from the anterior end of the endostyle, passes 
dorsally to meet its fellow in the mid-dorsal line just back of 
the ganglion. Thus united, the bands continue posteriorly 
to the opening of the oesophagus as the dorsal lamina. 

The endostyle now appears as a gutter-like structure, 
extending the entire length of the ventral side of the pharyn- 
geal chamber. A circle of branched tentacles form a crown 



A Simple Ttmicate. 139 

around the siphonal canal, just outside the peripharyngeal 
bands. 

Drawings should now be made of the structures thus shown 
on the interior of the pharynx. 

Carefully remove the ganglion together with the immedi- 
ately surrounding tissues, and examine it carefully in a watch 
glass. 

From its inner surface a funnel-shaped process will be 
observed. This is the dorsal tubercle^ and is a part of a 
small glandular mass, the neural gland. The course of the 
nerves can be readily determined by the adoption of the 
xylol method described for the nervous system of the Phyl- 
lopod Crustacea. 

Make a drawing of the ganglion and of its associated 
structures. 

General Remarks. — The outer covering of the Tuni- 
cates is variously described as the test, tunic, outer mantle, 
or sac. It varies considerably in different types, being in 
some delicate and transparent, in others tough and opaque. 
It is produced by the activity of a lining layer of epithelial 
cells, and is consequently comparable with the covering of 
many Invertebrates. It is peculiar in that it contains cellu- 
lose. The mantle or muscular sac (integument, second or 
inner muscular tunic) is also subject to considerable varia- 
tion. In life it is attached throughout to the inner surface 
of the tunic, though in alcohohc specimens it is often 
partially free. 

The Digestive System. — Food that is drawn into the 
pharyngeal sac by the activity of the cilia of the pharyngeal 
walls is collected by the mucus secreted, probably by the 
endostyle or by the sub-neural gland, and is carried along 



140 Invertebrate Zoology. 

the peripharyngeal bands to the dorsal lamina, and thence 
posteriorly along the " roof " of the pharyngeal sac to the 
opening into the oesophagus. In certain species the oesoph- 
agus opens into an enlarged stomach, and frequently 
accessory digestive glands are present. A median fold, the 
typhlosole^ partially divides the lumen of the intestine. 

The Excretory System. — Besides the renal organ 
already noted, there are certain small anomalous collec- 
tions of vesicles around the intestine and in the tunic that 
are supposed to perform excretory functions. The neural 
gland is also supposed by some to function as a renal organ. 

The Circulatory System. — In the Tunicata there are 
no true arteries or veins. The heart is a sac-like organ 
which forces the blood intermittently towards the posterior 
dorsal portion of the animal, and then in the opposite direc- 
tion towards the anterior ventral. It is surrounded by a 
fold, the peiicardium. During the respiratory circulation^ a ' 
ve7ttral trunk conveys the blood from the heart along the 
ventral portion of the animal, below the endostyle, and gives 
off lateral branches to the transvei'se vessels of the branchial 
sac. From these vessels the blood passes into the fine, 
irregularly disposed interstigmatic vessels, the meshes of 
which surround the stigmata. The longitudinal vessels in 
Molgula are arranged on the branchial folds already noted. 

When the current is from the ventral towards the dorsal 
portion of the animal, the blood passes through certain 
vessels to the mantle, the digestive and reproductive organs. 
The blood from these organs is then collected in a dorsal 
trunks which lies along the mid-dorsal line of the branchial sac, 
and from thence it passes into the transverse vessels. There 
are then, during this cycle, three systems, ist, Branchio- 



A Simple Tiniicate, 141 

cardiac^ conveying pure blood to the heart along the ven- 
tral trunk ; 2d, Cardio-splanchnic^ conveying blood from 
the heart to the viscera and other parts of the body ; 3d, 
SplancJmo-branchial^ conveying nnpure blood from the 
viscera, etc., through the dorsal trunk to the branchial 
sac. 

The test is supplied with blood through vessels that leave 
the main trunks near the heart. 

The Nervous System. — The nerves from the ganglion 
may be traced to certain sense-organs. The ocelli are sit- 
uated around the oral and cloacal orifices. The tentacles 
have already been noted. ^ 

The Reproductive System. —The Tunicata are her- 
maphrodite, though probably not self-fertilizing, as the ova ^ 
often reach maturity much earlier than the spermatozoa. 
In Molgula the ovary and testis unite and form a pair of 
hermaphrodite glands ; in other forms the glands may be 
separate. Reproduction by budding is not infrequent. 
This process may give rise to small colonies, the individuals 
of which may have a common circulatory system. Such 
Tunicates are called Social in distinction from the Solitary 
Tunicates, of which Molgula is a type. 

^ For a long time the dorsal tubercle was supposed to function as a 
sense-organ, and was called the olfactory tubercle. It is now known 
to be the funnel-shaped extremity of a ciliated duct, leading from 
the neural gland. It has been compared to the pituitary body of 
Vertebrates. 



APPENDIX. 



THE USE OF THE LABORATORY AND LABORA- 
TORY APPARATUS. 

Observance of the following regulations will facilitate lab- 
oratory work : — 

During laboratory hours work, walk, and talk quietly, that 
your co-laborers may not be annoyed. 

Handle microscopes and other instruments with care, 
keeping them clean and in order, and always, after using, 
return them to their proper places. 

Instruments that are the property of the laboratory should 
be used with especial care, and never retained longer than 
is necessary for the immediate work in hand. On returning 
the same, be sure that it is to the proper place. 

Reagents should be used sparingly, corks or stoppers 
returned to the bottles to which they belong, and the bottles 
returned to their proper places. Never pour back into the 
" stock bottle " any reagent that has been once made use of. 
Take care that your hands do not soil the label of the bottle. 
(It is well to wipe the lip of the bottle before and after 
pouring out the liquid.) 

143 



144 Invertebrate Zoology. 

After each day's work, clear up your table and return 
everything that has been borrowed. 

All organic refuse should be placed in the receptacle that 
has been provided for the same, and as free from liquid as 
possible. 

Pour nothing but hquid into the sinks. Be especially 
careful that sand and shreds of flesh are not left in the sinks. 

After using laboratory sponges, rinse them out and leave 
them in their racks. Never use them for absorbing grease 
or oil. 

Paraffin chips or wax should not be allowed to fall on the 
floor. 

Your own books, and certainly laboratory books, should 
not be handled with soiled fingers. 

Keep the lockers, drawers, etc., that have been assigned 
to you in an orderly condition. 

Finally, if you are so unfortunate as to injure laboratory 
instruments, books, or other property, inform the instructor 
of the extent of damage done. 



Appendix. 



HS 



B. 



LIST OF INSTRUMENTS AND REAGENTS. 



[Those marked with an asterisk should be owned by the student.] 



* Large scalpel. 

* Small scalpel. 

* Large tweezers, with serrated 

points. 

* Small tweezers, with smooth 

points. 

* Large scissors, with " lock " 

joint. 

* Small scissors, with fine points. 

* Vial of entomological pins. 

* Pair of needle holders and as- 

sorted needles. 

* Small package of bristles, white 

and black. 

* Hand lens or, better, a dissecting 

microscope. 

* Assortment of small brushes. 

* Drawing pencils, one hard and 

one medium. 

* Note book. 

* Erasing rubber. 

* Bristol drawing-board. 

* Slides and covers for micro- 

scopic work. 

GLASS WARE. 

* Several small and one large 

pipette. 
Water bottle. 



Assortment of hea\^ and light 

watch-glasses. 
Spirit-lamp. 

REAGENTS. 
50% alcohol. 
70%) alcohol. 
95% alcohol 
100% alcohol. 
Acidulated alcohol. 
Corrosive sublimate. 
Perenyi's fluid. 
Picro-sulphuric acid. 
10% nitric acid, 
x^ceto-carmine. 
Borax carmine. 
Alum cochineal. 
Alcohol carmine. 
Turpentine. 
Chloroform. 

Chloroform and paraffin. 
Collodion. 

Collodion and clove oil fixative. 
Clove oil. 
Cedar oil. 
Thyme oil. 
Canada balsam. 
Glycerine. 
Vaseline. 



146 Invertebrate Zoology, 

C. 

MICROSCOPES. 

The microscopes required for ordinary biological work 
should be " simple " and " compound." 

The simple inicroscope may be either a pocket lens or one 
of the more elaborate dissecting microscopes figured in cat- 
alogues of optical instruments, etc. Pocket lenses of a very 
convenient form are made in German silver mountings. For 
laboratory work each lens should be provided with a long- 
arm support, that it may be held, if need be, over a dissect- 
ing dish, allowing the free use of both the operator's hands. 

The compound microscope should be provided with eye- 
pieces and objectives that will give a magnifying power 
ranging from fifty to six or seven hundred diameters. The 
mechanical and optical parts of the microscope, and their 
uses, should be familiar to the student. The more impor- 
tant parts are as follows : The heavy foot, or base, often 
made in the shape of a horseshoe ; the upright pillar, which 
may be supplied with a joint, allowing inclination of the in- 
strument. The stage, generally black in color, is the hori- 
zontal support upon which the object to be examined is 
placed. The stage is often provided with a pair of com- 
pressors or clips, which need not be used in ordinary work. 
Immediately under the stage, and a part of it, is the sub- 
stage. The sub-stage is generally provided with a perforated 
apparatus — the diaphragm — for limiting the amount of 
light. In the more expensive instruments the sub-stage has 
also condensing glasses for increasing the intensity of the 
light. The 77iirror is provided with a plane and a concave 
surface. Though a more simple part of the instrument, the 



Appendix, 147 

mirror is most important. Successful observation frequently 
depends on the origin and intensity of the hght and also upon 
the direction from which the mirror throws light upon the 
object. The a7in of the microscope, reaching out from the 
pillar, supports more or less directly the tube^ which in turn 
carries, partly within itself, the draw -tube. The tube may 
be moved up and down either by a rack and pinion — 
" coarse adjiistmerit''' — or by shding easily through a collar 
supported by the arm. More delicate motion is secured by 
the use of the "fine adjustments^ a small milled wheel, gen- 
erally placed at the apex of the pillar. 

The parts of the microscope thus far mentioned are gen- 
erally included in the term " microscope stand.'* The opti- 
cal parts consist of a series of eye-pieces or octda7's, which fit 
into the upper part of the draw- tube, and a series of much 
more expensive objectives which screw into the lower end of 
the tube. A very convenient, though not essential, appara- 
tus is the triple nose-piece^ by means of which three objec- 
tives, revolving around a common centre, may be attached 
to the lower end of the tube, permitting an instantaneous 
change of magnifying powers. A little careful experiment- 
ing with the eye-pieces and objectives, under the direction 
of the instructor, will soon show their relative values as 
magnifying agents. One rule for adjusting the focus has no 
exceptions. "Always place the front of the objective near 
the object before looking in the ocular, and then move the 
tube upward in focussing." By observing this rule the objec- 
tive will not be ruined by being forced into the object. 

Objects may be examined as they float in watch-crystals, 
or they may be mounted on slides and covered with cover- 
glasses. 

In case objectives or oculars become soiled, it is well to 



148 Invertebrate Zoology, 

call the attention of the instructor. An objective may be 
ruined by being wiped with a dirty cloth. If, through acci- 
dent, fluid runs on to the stage of the microscope, be sure 
that it is all carefully removed from around the sub-stage. 
Be especially careful of acids, and do not let them long 
stand under the objective. Never wet the mirror. Do not 
allow the instrument to stand in strong sunlight. Always 
dust and put the instrument away after using. 



D. 

DIRECTIONS FOR DISSECTION. 

Very small objects are studied by '' teasing," which con- 
sists of gently tearing them apart under a lens, or of placing 
them under a cover-glass and tapping the cover lightly with 
a needle, the result being observed under the compound 
microscope. All teasing should be done while the object is 
covered with liquid, generally water, glycerine, or alcohol. 

With somewhat larger animals the small scissors, scalpel, 
and tweezers may be used, the object being pinned out 
under water. As the water becomes cloudy it should be 
renewed, or the cloudy portions may be removed with the 
large bulb-pipette. 

It is only the larger animals that are ordinarily dissected 
without being flooded with water. The sponge should be 
freely used and, if possible, the animal should be frequently 
placed under the tap. 

Nerves may generally be more easily separated from the 



Appendix, 149 

surrounding tissue if the specimen is allowed to stand for 
two or three days in 10% nitric acid. The acid, however, 
injures the other tissues. 

Muscles are generally more easily studied in alcoholic 
specimens. Small blood-vessels should be injected either 
with a pipette or with a hypodermic syringe. The use of 
strong acetic acid will frequently aid in separating organs 
that are firmly held together with connective tissue. 

Xylol may at times be advantageously used with small 
objects that have been preserved in strong alcohol. The 
xylol frequently clears the object in a most instructive way, 
presenting in the process one organ-system after another.^ 

Glycerine may be advantageously used as a teasing 
medium with many objects. Fragments of tissue thus iso- 
lated may be kept under the cover-glass for a considerable 
time. 

Schneider's aceto- carmine is a penetrating stain that can 
be used with fresh tissues, either during the process of teas- 
ing or after the objects are under the cover-glass. Material 
thus stained may be washed in water and kept for a short 
time by being mounted in glycerine. 

1 See page Z^i^ 



150 Invertebrate Zoology. 



METHODS OF KILLING, FIXING, AND HARDENING.i 

Unless animals or tissues are killed by some one of the 
recognized agents, they will not give the best histological 
results and the organs themselves will be often distorted and 
unnatural. The killing agents that are more ordinarily used 
are the following : Hot water (80° C), weak alcohol, corro- 
sive subUmate in hot or cold saturate solution, acetic acid, 
Kleinenberg's picro- sulphuric acid, Perenyi's fluid, and the 
varying chromic solutions. 

While the above reagents may be successfully used with 
many animals, there are nevertheless many organisms that 
violently contract on coming in contact with them. Such 
organisms must first be rendered insensible by being ansesthe- 
tized and then plunged into the killing agent. 

Chloral hydrate, weak alcohol, cocaine, chloroform, hydro- 
xylamine, etc., have been used as anaesthetizing agents. 

Objects that have been killed by the use of many of the 
above-mentioned agents are still soft and flabby and would, 
if allowed to remain for any considerable length of time, 
disintegrate. Several so-called *' fixing " and " hardening 
agents " have been adopted which are also frequently the 
same as are adopted for killing. Such are corrosive subli- 
mate, picro-sulphuric acid, Perenyi's fluid, and the chromic 
solutions. Alcohol, used in regularly increasing grades of 

^The methods of killing, fixing, hardening, preserving, staining, etc., 
are only given in the briefest possible way. It is taken for granted 
that the students have at hand either an instructor or the admirable 
text-books of microscopical technique which have been written by 
Dr. C. O. Whitman and A. B. Lee. 



Appendix. 1 5 1 

strength from 50 to 959^, is also frequently used as a fixing 
and hardening agent. To these might be added osmic 
acid and cupric sulphate. 

The length of time that objects should be allowed to 
remain in the fixing fluids varies according to the fluid used 
and the tissue or animal being treated. As a general rule, 
a large quantity of fluid, two or three times the bulk of the 
object, should be used, and this renewed as soon as it 
becomes cloudy. 

F. 

PRESERVATION. 

Objects that have been sufficiently fixed or hardened are 
thoroughly washed in water, excepting such as have been 
treated with picro-sulphuric acid or alcohol, and placed in 
709^ alcohol. An abundance of alcohol should always be 
used. Picro-sulphuric preparations should be repeatedly 
washed in alcohol of 70^ before being finally placed in the 
cabinet. 



METHODS OF STAINING. 

Organisms that when living are brightly colored are gen- 
erally bleached by the action of the fixing or preserving 
media, and tissues which are really very dissimilar in struc- 
ture not infrequently appear to be quite similar. To reveal 
these masked or hidden structures, microscopists have made 
use of certain stains. 

Stains are either diffuse or selective. The former dye the 
tissues throughout, while the latter stain only certain parts of 



152 Invertebrate Zoology. 

the tissue and leave other parts unaffected. Selective stains 
are for this reason spoken of as " differential stains." Cer- 
tain tissues will absorb a certain color in a certain fixed way 
and may be quite unaffected by another stain. 

The stains more commonly used are made from carmine, 
cochineal, haematoxylin, or from some of the numerous ani- 
line dyes. 

Stains are also either aqueous or alcoholic. Alcoholic 
specimens may be placed directly into alcoholic stain, but 
should be first washed with water before being placed in 
aqueous stain. The length of time that an object requires 
for proper staining depends on the object, the way it has 
been hardened, the length of time it has been preserved, and 
the stain that is adopted. 

The objects are taken from the alcoholic stains, washed 
in acidulated alcohol for a short time, and then placed, until 
wanted, in 70-90% alcohol. If an aqueous stain has been 
used, the excess of stain is washed out with water, often acid- 
ulated, and then the object is placed successively in 50, 70, 
and 90% alcohol. 

H. 
MOUNTING. 

Many small organisms, and portions of larger, may be 
mounted on glass slides and retained, if properly prepared, 
indefinitely. The mounting medium most commonly used is 
Canada balsam. The order of procedure is as follows : — 

The object, stained or unstained, is carried up through 
the grades of alcohol, and is finally placed in absolute alco- 
hol, that the last trace of water may be withdrawn from it. 
This is the process of dehydj-ating. 



Appendix. 1 5 3 

After dehydrating, the object is cleared, /.<f., an oil, which 
will mix with alcohol on the one hand and with Canada bal- 
sam on the other, is allowed to take the place of the abso- 
lute alcohol. This change for all small objects may be made 
by Hfting the object from the alcohol and, after draining off 
the excess of alcohol, placing the specimen for a few minutes 
in oil of clove, or oil of cedar, or turpentine, or organum oil. 
After remaining in the oil for a few moments, the object will 
become quite transparent. It is now ready to be placed on 
the slide and, after the oil is drained off, covered with a drop 
of Canada balsam. 

A clean cover-glass is now warmed for a moment over the 
spirit-lamp and allowed to gently rest on the balsam and 
object. If there is an excess of balsam, it may be removed 
with a cloth dampened with turpentine. If there is not a 
sufficient quantity of balsam, a drop may be placed on the 
slide near the edge of the cover, when it will run under by 
capillary attraction. 

If the object is rather thick and does not well support 
the cover-glass, the latter may be supported with rubber 
or glass rings made for the purpose, or with small pieces 
of a broken slide. " Wax feet " have been recommended by 
Kukenthal.^ 



I. 

METHODS OF IMBEDDING AND SECTION 
CUTTING. 

Though sections of certain tissues may ht cut without 
previous preparation, the best results are to be obtained by 
the adoption of one of the following methods : — 

1 To three parts of wax are added one part of vaseline and one part 
of Canada balsam. 



154 Invertebrate Zoology. 

The Paraffin Method. — The object, which should be 
of small size, not often exceeding i cu. cm., having been 
stained, is thoroughly dehydrated as previously directed. 

From absolute alcohol the object is to be placed in some 
fluid that will mix on the one hand with alcohol and on 
the other with paraffin. Such fluids are oil of cedar, oil of 
clove, oil of creosote, turpentine, chloroform, etc. Immer- 
sion for two hours in any one of these will often be sufficient. 

Flakes of paraffin are now whittled into the oil, or chloro- 
form, until the point of saturation is reached, and the speci- 
men allowed to stand for an hour or longer. If the fluid is 
warm, a less time may suffice. 

The object is now taken from the saturated oil or chlo- 
roform, and placed in melted paraffin, the temperature of 
which should not exceed 35° C. In from one to two hours' 
time the object will be thoroughly infiltrated. 

Make now a paper box, somewhat larger than the object, 
and by means of a warm pipette fill the box with paraffin, 
and place the object therein, noting the position in which it 
lies. 

In a few moments a film will have formed on the surface 
of the paraffin, when the box may be placed in a glass of 
water until thoroughly cold. 

Remove the box, wipe dry, and with a sharp knife trim 
off the paper from around the block of paraffin. Bearing in 
mind the position of the object when dropped into the box, 
scratch on the block a line that will designate the plane in 
which the object is to be sectionized. 

If the object is not to be immediately cut, it should be 
properly labelled and placed away for safe-keeping. 



Appe7idix, 155 

Objects imbedded in paraffin may be cut, by a steady 
hand, with no other instrument than a sharp razor. Of late 
years, however, some form of mechanical section-cutter — 
microtome — is to be found in every biological laboratory. 
Such microtomes are the Minot, which is the best for paraf- 
fin work, and the Thoma, which may be used for paraffin 
or for celloidin. 

If paraffin has been used as an imbedding mass, the 
object-holder, metal or wood, is warmed, and the block at- 
tached by cool water being allowed to run over block and 
holder until a firm union has been obtained. The position 
of the object in relation to the cutting-plane of the knife 
has, of course, been observed. 

Adjust the paraffin block, and cut off thin sections of par- 
affin until the neighborhood of the object is reached. Trim 
the remaining portion of the block so that it will be in the 
form of a cube, the edges of which are parallel to or at right 
angles with the cutting edge of the knife. Adjusting the 
gauge so that thin sections of equal thickness will be cut, 
proceed until as many sHces are secured as are needed. 

The following annoyances may arise : — 

I St. The sections roll. — Correct, by cutting thinner sec- 
tions, or by using softer paraffin, or by cutting in a warmer 
room. Sections sometimes roll when the knife is dull. 

2d. As the knife passes through the object, the tissue 
appears granular and the section porous. — The trouble is 
either that the imbedding was not properly done or the 
knife is not properly sharpened. 

3d. The block at its upper portion becomes white and 
broken. — See if the cutting edge is not set so that it is fur- 
ther from the block than the back part of the knife. 

4th. The sections crimp, the section of paraffin being 



156 Invertebrate Zoology, 

somewhat smaller in area than the block from which it is 
cut. — The sections are too thin, or the room is too warm, or, 
quite likely, the knife has become smeared with dirt or par- 
affin. Clean the knife on both sides by stroking it from the 
back toward the edge with a clean cloth dampened with 
chloroform. 

The Celloidin Method of Imbedding and Cutting. — 

The object is first stained in toto, dehydrated, infiltrated with 
thin, medium, and thick celloidin or collodion, and finally 
placed in a paper tray filled with the thick collodion. In a 
few minutes a film will form over the exposed surface of 
the collodion, when the paper tray and its contents are 
placed in a jar of strong chloroform, in which, after a few 
hours, the collodion becomes quite hard. 

The tray is now taken from the chloroform and, after the 
paper has been removed from the hardened block, the col- 
lodion with its enclosed object is placed in a vial of white 
oil of thyme or some similar oil. If the block of collodion 
is not large, in a few hours it will become as clear as glass, 
the stained object appearing as if suspended in a transparent 
fluid. 

For the process of orienting, the block of collodion may 
be taken from the oil, placed in a watch-crystal, and, after 
covering with the oil of thyme, examined with a lens or, if 
very small, with a compound microscope. The side of the 
block that is to be attached to the object-holder of the micro- 
tome is now selected, wiped dry of the oil, and immersed 
for a moment in ether, and then smeared with thick collo- 
dion. The object-holder, a block of wood rather than cork, 
is smeared in the same way, and the two coUodionized sur- 
faces are brought together. 



Appe7idix, 157 

The holder and collodion block are now immersed for a 
few minutes in chloroform, or long enough for them to 
become firmly united. 

The object-holder is finally screwed between the jaws of 
the microtome, and covered, by means of a camel's-hair 
brush, with oil of thyme. The microtome knife is flooded 
with the same oil. 

After a few sections have been cut from the block of col- 
lodion, the relative position of the plane of the knife to the 
axis of the object can be definitely established, and the 
object definitely oriented. 

The sections are now cut and may be at once transferred 
to the slide, covered with balsam, and mounted ; or if they 
are not immediately needed they may be kept indefinitely, 
together with the block, in a vial of thyme oil. 



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taught to compare these with others, and finally led to the 
principles or inductions growing out of the facts. 

Packard's Zoology. Briefer Course. viii4-338pp. i2mo. 

The distinctive characteristic of this book is its use of the 
object method. The author would have the pupils first examine 
and roughly dissect a fish, in order to attain some notion of 
vertebrate structure as a basis of comparison. Beginning 
then with the lowest forms, he leads the pupil through the 
whole animal kingdom until man is reached. As each of its 
great divisions comes under observation, he gives detailed 
instructions for dissecting some one animal as a type of the 
class, and bases the study of other forms on this. 

Packard's First Lessons in Zoology. Elementary 

Course, viii -j- 290 pp. i2mo. 

In scope this book differs considerably from those men- 
tioned above. Since it is meant for young beginners, it de- 
scribes but few types, mostly those of the higher orders, anu 
discusses their relations to one another and to their surround- 
ings. The aim, however, is the same with that of tlie others ; 
namely, to make clear the general princii)les of the science, 
rather than to fill the pupil's mind with a mass of what may 
appear to him unrelated facts. Classification is fully treated. 



Henry Holt Sr Co. 



Martin's The Human Body. Advanced Course. 

By H. Newell Martin, sometime Professor in the Johns Hopkins 
University, xvi 4-621+34 pp. 8vo. Copies without the Appendix on 
Reproduction will be supplied when specially 07-dered. 

While intelligible to the general reader, it is accurate and 
sufficiently minute in details to meet the requirements of 
students who are not making human anatomy and physiol- 
ogy subjects of special advanced study. Wherever it has 
seemed really profitable, hygienic topics have been discussed. 
The work is in use in such medical schools as those of Harvard 
University and the University of Michigan. 

Martin's The Human Body. Briefer Course. 

xii +377 pp. i2mo. With a chapter 07t Stimulants ajtd Narcotics. 

A clear, accurate, and coherent statement of the ascertained 
facts of human physiology, so treated as to make this branch 
of natural science a source of discipline to the observing and 
reasoning faculties, and not merely a mass of detail useful to 
know, which the pupil is to learn by heart. So far as is prac- 
ticable in an elementary treatise, the facts are exhibited as 
illustrations of, or deductions from, the doctrine of the Con- 
servation of Energy and that of the Physiological Division of 
Labor. The discussions are supplemented by simple directions 
for demonstrating the fundamental truths of the science. 

Martin's The Human Body and the Effects of 

Narcotics. viii + 399pp. i2mo. 

An edition of the foregoing book in which, at the solicitation 
of the Woman's Christian Temperance Union, the matter 
relating to narcotics has been rearranged and augmented. 

Martin's The Human Body. Elementary Course. 

vi-l-261 pp. i2mo. 

A simple and accurate outline of those broad facts con- 
cerning the structure and actions of the living human body 
which make clear the reasons, as regards health, for following 
or avoiding certain courses of conduct. The action on the 
body of stimulants and narcotics is fully treated. 



The American Science Series. 



7 



James's Principles of Psychology. Advanced Course. 

By William James, Professor of Psycholog-y in Harvard University. 
Vol. I., xii4-689 pp. Vol. 11., vi4-704 pp. 8vo. 

Treats psychology from the point of view of natural science, 
leaving strictly metaphysical questions in abeyance. The 
works on psychology of the older school give little or no 
account of the facts recently brought to light in the laboratory. 
Recent works on physiological psychology, on the other hand, 
give an abundance of physical facts, but fail to trace much 
connection between them and mental laws. In this book 
experimental facts and theoretical inferences are treated of in 
combination, so as to give to each of the successive topics a 
rounded form, and to avoid pure anatomy and physiology on 
the one hand, and on the other pure metaphysics. 

E. H. Griffin, Johns Hopkins 
University: — An important con- 
tribution to psychological science 



ing suggestions. To me the best 
treatment of the whole matter of 
advanced psychology in existence. 
It does more to put psychology in 
scientific position both as to the 
statement of established results and 
a stimulating to further problems 
and their treatment, than any other 
book of which I know. 



discussing its present aspects and 
problems with admirable breadth, 
insight, and independence. 

John Dewey, University of Mi- 
chigan : — A remarkable union of 
wide learning, originality of treat- 
ment, and, above all, of never-fail- 

James's Psychology. Briefer Course. 

xiii-|-478 pp. i2mo. 

This is not simply an abridgment of the ^* Principles of 
Psychology." About two fifths of the book is either v.tw or 
rewritten. All the polemical and historical matter and purely 
speculative passages of the larger work have been omitted. 
Brief chapters on the various senses have been added. The 
purpose has been to make the book directly available for 
class-room use. 



H. N. Gardiner, Professor in 
Smith College, Mass : — It is within 
the simple truth to say that a belter 
text-book of psychology for college 
use, one clearer, simpler, more 
stimulating, does not exist. 



Williston Hough, Professor in 
the University of Alinnesota: — 
This is the book we have been 
wailing for — a competent, authori- 
tative treatment of physiological 
psychology which is suitable for 
use as a text-book. 



8 Henry Holt Sr Co. 



Walker's Political Economy. Advanced Course. 

By Francis A. Walker, President of the Massachusetts Institute of 
Technology, viii -[- 537 pp. 8vo. Revised and Ejtlarged. 

The peculiar merit of this book is its reality. The reader is 
brought to see the application of the laws of political economy 
to real facts. He learns the extent to which those laws hold 
good, and the manner in which they are applied. The subject 
is divided, as usual, into the three great branches of pro- 
duction, exchange, and distribution. An interesting and 
suggestive " book " on consumption is added which serves to 
bring in conveniently the principles of population. The last 
part of the volume is given to the consideration of various 
practical applications of economic principles. 

Walker's Political Economy. Briefer Couise. 

viii -f 415 pp. i2mo. 

The demand for a briefer manual by the same author iror 
the use of colleges in which only a short time can be given to 
the subject has led to the publication of the present volume. 
The work of abridgment has been effected mainly through 
excision, although some structural changes have been made, 
notably in the parts relating to distribution and consumption. 

Walker's First Lessons in Political Economy. 

Elementary Course. x-f-332pp. i2mo. 

This book is addressed to pupils fifteen or sixteen years of 
age. What has been attempted is a clear arrangement of 
topics ; a simple, direct, and forcible presentation of the ques- 
tions raised ; the avoidance, as far as possible, of certain 
metaphysical distinctions which the author has found per- 
plexing ; a frequent repetition of cardinal doctrines, and 
especially a liberal use of concrete illustrations, drawn frojii 
facts of common experience or observation. 

HENRY HOLT & CO., Publishers, N. Y. 



LIBRARY OF CONGRESS 




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